WORLD TRADE  
ORGANIZATION  TN/TE/W/50/Rev.1 
4 July 2006 
 
 (06-3234) 
Committee on Trade and Environment 
Special Session Original:   English 
 
 
 
CANADA'S REVISED LIST OF ENVIRONMENTAL GOODS 
 
Submission by Canada  
 
Paragraph 31 (iii)  
 
Revision  
  
 The following communication, dated 3 July 2006,  is being circulated at the request of the 
Delegation of Canada
. 
 
_______________  
 
 
I. INTRODUCTION 
1. The Committee on Trade and Environment in Special Session has devoted significant time 
and energy to a discussion of environmental goods under Paragraph 31(iii) of the Doha Ministerial 
Declaration.  Canada notes that considerable progr ess has been achieved.  To help maintain this 
momentum, and further the negotiations at this criti cal juncture, Canada is submitting this revision to 
our list of environmental goods.  This revisi on is without prejudice to our position as these 
negotiations proceed. 
2. Canada continues to believe that substantia lly improving market access for environmental 
goods through the reduction or, as appropriate, elimina tion of tariffs and non-tariff barriers will ensure 
a “triple win” outcome for all WTO Members a nd an important contribution to sustainable 
development.  This will be achieved through redu ced costs to importing countries for products and 
technologies utilized to improve domestic environmenta l conditions and to manage natural resources.  
We are particularly interested in ensuring that  developing country Members’ participation is 
meaningfully reflected in the outcome of these negot iations, and seek to have their interests reflected 
in a multilaterally agreed set of environmental goods.  Canada’s revised list takes this objective into 
account. 
II. ENVIRONMENTAL GOODS NEGOTIATIONS POST-HONG-KONG 
3. Since the Ministerial meeting in Hong K ong in December 2005, the CTESS has held one 
formal meeting and three informal sessions.  Ca nada has greatly benefited from the information 
exchanges at these meetings. 
4. At the meeting on 21-22 February, Members ex changed views on indicative parameters that 
could guide future discussions under Paragraph 31 (iii), as well as the categories to which these 
parameters could be applied.   The categories of  Renewable Energy and Air Pollution Control were 
selected for the technical discussion of 4-5 April 20 06.  Canada submitted a non-paper (JOB(06)/73) TN/TE/W/50/Rev.1 
Page 2  
 
  outlining the environmental benefits of goods in th ese categories.  We outlined cross-cutting issues 
such as technology transfer in relation to enviro nmental goods.  Other cro ss-cutting issues such as 
special and differential treatment, non-tariff barriers a nd transfer of technology have been highlighted 
as important questions to address in the context of these discussions.  Canada has stated that it is 
prepared to respond to proposals from other Members on these issues.  
5. A second technical discussion was held 10- 12 May 2006 to examine products in the 
categories of Waste Water Management and Solid  and Hazardous Waste Management.  A third 
informal meeting was held 12-13 June 2006, to discuss goods in the remaining categories of 
(i) environmental monitoring, analysis and assessmen t equipment;  (ii) remediation and clean up of 
soil and water;  (iii) cleaner tec hnology and products;  (iv) environm entally preferable products based 
on end use or disposal characteristics;  (v) hi gh environmental performance or low environmental 
impacts;  (vi) and others (Noise and Vibration Abatement; Resource Management; Heat and Energy 
Management; Natural Risk Manage ment; Potable Water Treatment; Recycling Systems; and Soil 
Conservation).   
III. ISSUES IDENTIFIED  
6. Canada provided detailed explan ations on the environmental a nd developmental aspects of 
products in the various categories identified.  We found the discussions to be particularly helpful.  
We responded to many useful specific questions  on the products on our list and learned from 
responses to questions on goods in lists of other Memb ers.  These deliberations have helped us in the 
review of our list and to evaluate the merits  of products nominated by other Members. 
The relationship between environmental goods and services 
7. Regarding the linkages between environmenta l goods and services, as Canada has outlined 
previously, many environmental activities entail the delivery of services in conjunction with the use of 
goods.  Canada is actively pursuing further liberalizat ion of a wide range of environmental services in 
the context of on-going negotiations on services.  Ou r list of goods continues to be informed by the 
types of products used in environmental servi ces, and Canadian officials working in the two 
areas compare notes on an on-going basis in order to  identify synergies and to ensure a mutually 
supportive approach.  We would encourage Member s expressing concerns that these negotiations are 
disconnected to participate more actively in th e on-going negotiations on environmental services. 
Single versus dual-use  
8. Canada submitted a non-paper on products in th e categories of Renewable Energy and Air 
Pollution Control. We examined the products that we  had nominated to identify the context in which 
the good would be used, and we considered the issu e of single versus multiple use and the parameters 
that the Chair had identified at the February mee ting.  We supplemented these to ask a number of 
basic questions for each product, including:  Does the product have a clear environmental use/benefit 
and other considerations such as the 3Rs or life cycle impacts?  
9. On the identification of single-use goods as an  exercise to advance the negotiations, Canada 
argued that identifying single environmental use goods is not a helpful parameter when used in 
isolation.  We argued that there are many en vironmental goods that may have non-environmental 
uses.  The main question was the relative impor tance of the good in addressing an environmental 
issue, and whether the non-environmental use of the good was benign. 
10. Some Members have argued that these negotiations need to be more balanced and that a more 
‘holistic’ view of environmental goods  is required.  We agree.  With  this in mind, we would suggest 
that excluding dual use items from the negotiation by applying the criterion of ‘single end-use’ would  TN/TE/W/50/Rev.1 
 Page 3 
 
 
  not seem to be in keeping with a balanced appr oach to these negotiations.  On the contrary, the 
‘single-use’ criterion reflects only the trade interest.  Canada has argued, therefore, that it is more appropriate to consider other factors as well, su ch as the environmental benefits of the product. 
Product coverage 
11. Canada has noted that we could likely accept ma ny, but not all, products that have been 
proposed by Members to date as environmental goods .  While some Members have argued that it will 
be impossible to achieve consensus on parameters to identify environmental goods, in Canada’s view, 
we see the exercise as “peer review pr ocess” that can lead to consensus.  We are of the view that there 
is considerable commonality among the types of  environmental goods proposed to date.   
12. Of course, Members will attach varying degrees of priority to selected goods proposed. 
Canada has indicated its willingness to be flexible in identifying environmental goods.  We also wish 
to reiterate our support for the ‘living list’ appr oach proposed by New Zealand for emerging goods 
and to ‘park’ goods that may need further analysis or discussion.   
Development Aspects of Environmental Goods 
13. Canada has outlined previously that we see  environmental goods as the tools to achieve 
multiple environmental objectives such as pollution re mediation, energy and resource conservation, 
and to achieve domestic and internationally agreed  environmental goals. Environmental goods can be 
used to improve local environmental conditions whic h in turn can lead to improved living conditions 
and conservation of scarce natural resources. Contrary  to what some Members have argued, many of 
the environmental goods are ‘low tech’ affordable products, or may be ‘high tech’, but are readily 
accessible and affordable solutions to environmental problems. 
Transfer of Technology  
14. Canada cited examples of Canadian aid and t echnical assistance, combined with commercial 
interests, particularly among small and medium-s ized enterprises, that contribute to technology 
transfer of environmental goods.  In particular , we highlighted numerous examples of renewable 
energy and other projects in which Canadian smal l and medium-sized enterprises were partnering 
with similar companies and research organizations in  developing counties.  We also outlined that 
there are numerous examples of private investment  and voluntary national a nd international programs 
to assist in this sort of technology transfer.  We underscored that there are numerous examples of how 
technology transfer can take place through aid and other means.  An issue for Canada is that the rules 
for liberalizing trade in environmental goods must be non-discriminatory, predictable and transparent. 
Impacts on small and medium-sized enterprises in  both developed and deve loping countries are a 
concern for us. 
IV. CANADA’S REVISED LIST OF ENVIRONMENTAL GOODS 
15. Canada had included a number of chemicals a nd recyclable materials in its initial list.  
We presented these items because, in our view, they  have the potential to contribute to a better 
environment.  For example, recy clable material can be used to produce new goods, diverting waste 
from landfills, requiring less energy and releasing less  greenhouse gas emissions than primary inputs.  
Some chemicals were proposed because they are ke y components in waste water treatment facilities.  
At the same time, we outlined that these environm ental benefits could be achieved only when such 
items are managed in an environmentally sound manner throughout the life cycle. 
 TN/TE/W/50/Rev.1 
Page 4  
 
  16. During the course of the Committee’s informal me etings in the last few months, we took 
careful note of the comments and concerns raised . With a view to demonstrate that a common 
identification is being developed in this committee,  Canada has removed all recyclable material and 
chemicals from our list of environmental goods.  It is clear that these goods do not have the requisite 
consensus in the negotiations to be included in any agreed list of environmental goods.  We are 
looking forward to further progress and intensifica tion of the negotiations under paragraph 31(iii).    TN/TE/W/50/Rev.1 
 Page 5 
 
 
   
HS 
CODE PRODUCT DESCRIPTION                      ADDITIONAL PRODUCT 
SPECIFICATION 
AIR POLLUTION CONTROL 
840410 Auxiliary plant for use with boilers of heading 84.02 
or 84.03 (for example, economizers, super-heaters, soot removers, gas recoverers); condensers for steam or other vapour power units    
840420 Condensers for steam or other vapour power units   
840510 Producer gas or water gas generators, with or without 
their purifier; acetylene gas generators and similar water process gas generator, with or without their purifiers Include only those with purifiers 
841410 Vacuum pumps   
841459 Fans (and blowers) other than table, floor, window, 
ceiling or roof fans with a self contained electric 
motor of an output not exceeding 125W   
841480 Air or vacuum pumps, air or other gas compressors 
and fans; ventilating or recy cling hoods incorporating 
a fan, whether or not fitted with filters; other   
841490 Parts of vacuum pumps, compressors, fans, blowers, 
hoods   
841780 Other industrial or laboratory furnaces and ovens, 
including incinerators, non-electric  Waste incinerators  
841960 Machinery for liquefying air or other gases    
841989 Machinery, plant and equipment whether or not 
electrically heated, for the treatment of materials by a process involving a change of temperature such as heating, vapourizing, condensing or cooling (excl. machinery or plant used for domestic purposes and 
machinery and appliances specified elsewhere)   
851410 Industrial or laboratory furnaces and ovens; electric, 
resistance heated  Waste incinerators or other waste 
treatment apparatus 
851420 Industrial or laboratory furnaces and ovens; electric, 
induction or dielectric  Waste incinerators or other waste 
treatment apparatus 
851430 Industrial or laboratory furnaces and ovens, electric, 
other  Waste incinerators or other waste 
treatment apparatus TN/TE/W/50/Rev.1 
Page 6  
 
  HS 
CODE PRODUCT DESCRIPTION                      ADDITIONAL PRODUCT 
SPECIFICATION 
851490 Parts of industrial or laboratory electric furnaces and 
ovens or other laboratory induction or dielectric heating equipment  Parts of waste incinerators 
841790 Parts of industrial or laboratory furnaces and ovens, 
including incinerators, non-electric  Parts of waste incinerators  
WASTE WATER MANAGEMENT 
730900 Reservoirs, tanks, vats & sim ctnr, cap >300L,i o s (ex 
liq/compr gas type)    
731010 Tanks, casks, drums, cans, boxes and similar 
containers, of iron or steel, for any material, of a capacity of >= 50 l but =< 300 l, not elsewhere specified (excl. containers for compressed or liquefied 
gas , or containers fitted with mechanical or thermal 
equipment, products)    
731021 Cans of iron or steel, of a capacity of < 50 l, which are 
to be closed by soldering or crimping (excl. containers for compressed or liquefied gas)    
731029 Tanks, casks, drums, cans, boxes and similar 
containers, of iron or steel, for any material, of a capacity of < 50 l, not elsewhere specified (excl. containers for compressed or liquefied gas, or 
containers fitted with mechanical or thermal 
equipment, and cans)    
841320 Hand pumps not elsewhere specified, o/t those of 
subheading No 8413.11 or 8413.19    
841350 Reciprocating positive displacement pumps not 
elsewhere specified   
841360 Pumps for liquids, whether or not fitted with a 
measuring device; other rotary positive displacement pumps Hydraulic fluid power pumps, 
vane type Roller Pumps 
841370 Pumps for liquids, whether or not fitted with a 
measuring device; other centrifugal pumps Centrifugal pumps lined to 
prevent corrosion; centrifugal 
sewage pumps 
842199 Parts of filtering or purifying machinery and 
apparatus for liquids or gases     TN/TE/W/50/Rev.1 
 Page 7 
 
 
  HS 
CODE PRODUCT DESCRIPTION                      ADDITIONAL PRODUCT 
SPECIFICATION 
848110 Valves, pressure reducing Filter-regulators and filter 
regulator-lubricators / Other, 
pneumatically controlled / 
Hydraulically controlled 
848130 Valves, check   Of iron / Of steel  
848140 Valves, safety or relief       
848180 Other appliances for pipes, boiler shells, tanks, vats or 
the like  Hand operated or hand activated 
of iron - Gate type and globe type 
848190 Parts of valves and similar articles for pipes, boiler 
shells, tanks, vats or the like, not elsewhere specified     
SOLID/HAZARDOUS WASTE MANAGEMENT 
854330 Machines elsewhere specified & apparatus for 
electroplating, electrolysis or electrophoresis  Chloralkali electrolyser cells  
841790 Parts of furnaces, non-electric Parts of waste incinerators 
842220 Machinery for cleaning or drying bottles or other 
containers   
842381 Other weighing machinery having a  maximum 
weighing capacity not exceeding 30 kg    
842382 Other weighing machinery having a maximum 
weighing capacity exceeding 30kg but not exceeding 5,000 kg   
842389 Other weighing machinery not elsewhere specified   
847989 Machines elsewhere specified & mechanical 
appliances not elsewhere specified having individual functions In-vessel composting systems / 
Radioactive waste press / Trash 
compactors / Other 
847990 Parts of machines elsewhere specified and mechanical 
appliances having individual  functions, not elsewhere 
specified or included in this chapter  Parts of trash compactors 
850590 Electromagnets; other, including parts Electromagnet 
901320 Lasers, other than laser diodes    TN/TE/W/50/Rev.1 
Page 8  
 
  HS 
CODE PRODUCT DESCRIPTION                      ADDITIONAL PRODUCT 
SPECIFICATION 
REMEDIATION/CLEAN-UP OF SOIL AND WATER 
890710 Inflatable rafts Inflatable oil spill recovery 
barges 
890790 Other floating structures Pollution protection booms, oil 
absorbent booms 
ENVIRONMENTAL MONITORING, ANALYSIS AND ASSESSMENT EQUIPMENT 
350790 Enzymes not elsewhere specified; prepared enzymes 
not elsewhere specified   
381500 Reaction initiators, reaction accelerators and catalytic 
preparations, not elsewhere specified or included. 
(3815)   
382200 Composite diagnostic or laboratory reagents, not 
elsewhere specified    
690310 Other refractory ceramic goods ( e.g.. retorts, 
crucibles, muffles, nozzles, plugs, supports, cupels, tubes, pipes, sheaths, rods) - containing more than 50 % graphite, other forms of carbon or a mixture of these products                                       
Laboratory refractory equipment  
690320 Other refractory ceramic goods ( e.g.. retorts, 
crucibles, muffles, nozzles, plugs, supports, cupels, 
tubes, pipes, sheaths, rods) - containing by weight more than 50 % of alumina or of a mixture or compound of alumina and of silica   Laboratory refractory equipment  
690390 Other refractory ceramic goods (e.g.. retorts, 
crucibles, muffles, nozzles, plugs, supports, cupels, tubes, pipes, sheaths, rods) - other                    Laboratory refractory equipment  
690919 Other ceramic wares for chemical or other technical 
uses Laboratory refractory equipment  
700800 Multiple-walled in sulating units of glass   
701710 Laboratory, hygienic or pharmaceutical glassware, 
whether or not graduated or calibrated; of fused quartz or other fused silica     TN/TE/W/50/Rev.1 
 Page 9 
 
 
  HS 
CODE PRODUCT DESCRIPTION                      ADDITIONAL PRODUCT 
SPECIFICATION 
701720 Laboratory, hygienic or pharmaceutical glassware, 
whether or not graduated or  calibrated; of other glass 
having a linear coefficient of expansion not exceeding 5 X 10 
-6 per Kelvin within a temperature range of 0 C 
- 300 C   
701790 Laboratory, hygienic or pharmaceutical glassware, 
whether or not graduated or calibrated; other   
841990 Parts of machinery, plant and equipment of heading 
No 84.19   Medical, surgical or laboratory 
stabilizers 
842119 Centrifuges, including centrifugal dryers other than 
cream separators and clothes-dryers   
842121 Filtering or purifying machinery and apparatus for 
liquids: for filtering or purifying water   
842129 Filtering or purifying machinery and apparatus for 
liquids; other  Hydraulic fluid power filters 
rated at 1,000 kPa or greater  
842139 Filtering or purifying machinery and apparatus for 
gases; other  Catalytic converters / Gas 
separation equipment / Pneumatic 
fluid power filters rated at 550 
kPa or greater / Industrial gas 
cleaning equipment / 
Electrostatic filters (precipitators)  
842191 Parts of centrifuges, including centrifugal dryers Centrifuges, accessories & parts; 
except clothes dryers and clothes 
dryer furniture 
901540 Photogrammeterical surveying instruments and 
appliances   
901580 Other instruments and appliances used in geodesy, 
topography, hydrography, oceanography, hydrology, meteorology or geophysics (excl. compasses, rangefinders, theodolites, tacheometers )    
901590 Parts and accessories for instruments and appliances 
used in geodesy, topography, photogrammetrical surveying, hydrography, oceanography, hydrology, meteorology or geophysics, and for rangefinders not 
elsewhere specified Photogrammetric instruments; 
parts and accessories for articles 
of subheading 901540 
902229 Apparatus based on the use of alpha, beta, or gamma 
radiations, for other uses    TN/TE/W/50/Rev.1 
Page 10  
 
  HS 
CODE PRODUCT DESCRIPTION                      ADDITIONAL PRODUCT 
SPECIFICATION 
902290 Apparatus based on the use of X-rays or of alpha, 
beta, or gamma radiations for other than medical, surgical, dental or veterinary uses  Parts and accessories for goods of 
subheading 902229 
902511 Thermometers and pyrometers, not combined with 
other instruments: liquid-filled, for direct reading  Clinical thermometers  
902519 Thermometers and pyrometers, not combined with 
other instruments: other than liquid-filled, for direct reading Clinical thermometers / 
Pyrometers   
902580 Hydrometers and similar floating instruments, 
thermometers pyrometers, barometers, hygrometers, and psychrometers, recording or not, and  any 
combination of these instruments  Barometers, not combined with 
other instruments  
902590 Parts and Accessories for Hydrometers and similar 
floating instruments, thermometers pyrometers, barometers, hygrometers, and psychrometers, recording or not, and any combination of these instruments  Other thermometers and 
pyrometers, not combined with 
other instruments, excluding 
liquid filled for direct reading  
902610 Instruments and apparatus for measuring or checking 
the flow or level of liquid  Electrical flow meters  
902620 Instruments and apparatus for measuring or checking 
pressure  Electrical instruments and 
apparatus  
902680 Other instruments and apparatus  Electrical heat meters  
902690 Parts and accessories for ar ticles of subheading 9026    
902710 Gas or smoke analysis apparatus   
902720 Chromatographs and electrophoresis instruments  Gas chromatographs / Liquid 
chromatographs / Electrophoresis 
instruments  
902730 Spectrometers,  Spectrophotometers and 
Spectrographs Using Optical Radiations (Ultraviolet, Visible, Infrared)   
902740 Exposure Meters  Exposure meters  TN/TE/W/50/Rev.1 
 Page 11 
 
 
  HS 
CODE PRODUCT DESCRIPTION                      ADDITIONAL PRODUCT 
SPECIFICATION 
902750 Other instruments and apparatus using optical 
radiations (UV, visible, IR) Thermal analysis instruments and 
apparatus / Other chemical 
analysis Photometers instruments 
and apparatus / Other chemical 
analysis instruments and 
apparatus 
902780 Other instruments and apparatus for physical or 
chemical analysis  Nuclear magnetic resonance 
instruments / Mass spectrometers 
/ Electrochemical analysis 
instruments and apparatus / 
Chemical analysis instruments 
and apparatus / Physical analysis 
instruments and apparatus  
POTABLE WATER TREATMENT 
391400 Ion-exchangers based on polymers of Nos 39.01 to 
39.13 in primary forms   
841381 Pumps for liquids, whether or not fitted with a 
measuring device; other pumps Wind turbine pump 
RECYCLING SYSTEMS 
841940 Distilling or rectifying plant     
847410 Sorting, screening, separating or washing machines 
elsewhere specified   
RENEWABLE ENERGY PLANT 
841011 Hydraulic turbines elsewhere specified and water 
wheels of a power not exceeding 1,000 kW   
841012 Hydraulic turbines elsewhere specified and water 
wheels of a power exceeding 1,000 kW but not exceeding 10,000 kW    
841013 Hydraulic turbines elsewhere specified and water 
wheels of a power exceeding 10,000 kW Hydraulic turbines elsewhere 
specified - Francis type / Other 
841090 Hydraulic turbines elsewhere specified and water 
wheels; parts, including regulators   
850231 Other electric generating sets Wind-powered  
854140 Photovoltaic diodes  Photosensitive diodes / Solar 
cells  TN/TE/W/50/Rev.1 
Page 12  
 
  HS 
CODE PRODUCT DESCRIPTION                      ADDITIONAL PRODUCT 
SPECIFICATION 
902790 Microtomes; parts and accessories Microtomes  
902890 Parts and accessories for ar ticles of subheading 9028  Of gas meters / Of liquid meters  
903010 Instruments and apparatus for measuring or detecting 
ionising radiations   
903020 Cathode-ray oscilloscopes and cathode-ray 
oscillographs   
903031 Multimeters   
903039 Other instruments and apparatus, for measuring or 
checking voltage, current, resistance or power, 
without a recording device  For measuring or checking 
voltage, current or resistance  
903083 Other instruments and apparatus for measuring or 
checking electrical quantities, with a recording device   
903089 Other instruments and apparatus for measuring or 
checking electrical quantities    
903090 Parts and accessories (for nominated articles of 
subheading 9030)   
903110 Machines elsewhere specified for balancing 
mechanical parts    
903120 Test benches    
903130 Profile projectors   
903149 Other optical instruments, appliances and machines 
elsewhere specified for measuring or checking   
903180 Other measuring or checking instruments, appliances 
and machines elsewhere specified, not elsewhere 
specified in this chapter For testing electrical 
characteristics of internal 
combustion engines elsewhere 
specified  
903190 Parts and accessories (for nominated articles of 
subheading 9031)    
903210 Thermostats   
903220 Manostats   
903281 Hydraulic and pneumatic  instruments and apparatus Industrial process control 
instruments and apparatus             TN/TE/W/50/Rev.1 
 Page 13 
 
 
  HS 
CODE PRODUCT DESCRIPTION                      ADDITIONAL PRODUCT 
SPECIFICATION 
903289 Automatic regulating or controlling instruments, other Temperature control instruments 
/ Pressure and draft control 
instruments / Flow and liquid 
level control instruments / 
Humidity control instruments / 
Automatic voltage and voltage-
current regulators  / Control 
instruments for air-conditioning, 
refrigeration or heating systems      
903290 Parts and accessories - automatic regulating or 
controlling instruments    
903300 Parts and accessories (not specified or included 
elsewhere in this Chapter) for machines elsewhere specified, appliances, instruments or apparatus of 
Ch. 90   
HEAT AND ENERGY MANAGEMENT 
841919 Other instantaneous or storage water heaters, non-
electric Solar water heaters 
841950 Heat exchange units    
853080 Other electrical signalling, safety or traffic control 
equipment    
853931 Discharge lamps, fluorescent, hot cathode    
902810 Gas meters    
902820 Liquid meters    
902830 Electricity meters    
SOIL CONSERVATION 
460120 Mats, matting, and screen s of vegetable materials  Erosion control matting 
(biodegradable)  TN/TE/W/50/Rev.1 
Page 14  
 
  HS 
CODE PRODUCT DESCRIPTION                      ADDITIONAL PRODUCT 
SPECIFICATION 
CLEAN TECHNOLOGIES, PROCESSES AND PRODUCTS 
382490 Products, preparations and residual products of the 
chemical or allied industries, incl. those consisting of 
mixtures of natural products, n.e.s . (excl. binders for foundry moulds and cores; naphthenic acids, their water-insoluble salts and their esters; non-agglomerated metal carbides mixed together or with 
metallic binders; prepared additives for cements, 
mortars and concretes; non-refractory mortars and concretes; sorbitol) Fatty substances of animal or 
vegetable origin and mixtures 
(biodiesel)  
850680 Primary cells & batteries  Fuel cells  
  
__________