In typesetting, a slug is a piece of lead or other type metal, in any of several specific word senses.
 In one sense, a slug is a piece of spacing material used to space paragraphs.
 In the era of commercial typesetting in metal type, they were usually manufactured in strips of 6-point lead.
 In another sense, a slug is one line of Linotype typeset matter, where each line corresponds to one piece of lead.
Document retrieval is defined as the matching of some stated user query against a set of free-text records.
 These records could be any type of mainly unstructured text, such as newspaper articles, real estate records or paragraphs in a manual.
 User queries can range from multi-sentence full descriptions of an information need to a few words.
TMK 201 is a type of four-axle tramcar produced by the Đuro Đaković factory (from Slavonski Brod) that operates in the capital of Croatia, Zagreb.
 Previously, it was also used in Belgrade from 1970 to 1991.
 The first tram of this type was received by ZET (the city public transportation company in Zagreb) on December 31, 1973, and the thirtieth-and-last of the type was delivered in June 1974.
 The new tram model was first put in service on January 22, 1974.
 Eighteen vehicles remain actively involved in the transport of passengers, and some were used for the production of TMK 2100 in the 1990s.
AV8 Air was an airline based in the United Kingdom.
 It was established in June 2003 and started operations on 25 November 2003.
 It was launched as a subsidiary of tour operator CT2 and began operations on 7 April 2004 with a long-haul flight to Cape Town using a Boeing 767-300ER aircraft.
 The company operated the 767 on a damp lease basis from Icelandair until their own Air Operator's Certificate (AOC) was granted from the UK Civil Aviation Authority (CAA).
 Unfortunately, due to a lack of a bond, the AOC was revoked.
 A Boeing 757-200 aircraft was intended for use on short-haul flights to Mediterranean resorts, but due to the unsuccessful AOC application, the aircraft was only operated on a weekly check flight around Manchester.
 The airline ceased trading after only five months.
A transportation library is a type of library designed to support the study, research, and dissemination of information related to transportation.
 A transportation library provides resources related to policy, regulations, operations, and other aspects of transportation.
 Users of transportation libraries include engineers, city planners, contractors, academic researchers, and the general public.
 Transportation libraries are located at the federal, state, and local levels of government, as well as at universities and research institutes. Major transportation libraries can be found in the United States, Canada, the United Kingdom, Sweden, Australia, and Japan.
A reglet is a piece of wooden spacing material used in typesetting, usually to provide spacing between paragraphs, though it is sometimes used to fill in small spaces not taken up by type in the chase.
Icelandair is the main airline of Iceland, headquartered at Keflavík International Airport in Iceland.
 It is part of the Icelandair Group and, in the middle of 2015, operated scheduled services to 39 cities in 16 countries on both sides of the Atlantic Ocean out of its hub at Keflavík International Airport.
 The geographical position of Iceland allows one-stop transatlantic flights, which are one pillar of the airline's business strategy, along with traffic to and from the country.
Rachel of Kittery, Maine (?
-1695) was an African-American enslaved woman in the New England state of Maine, who was murdered by her enslaver, Nathaniel Keen, who was subsequently put on trial on for murder.
 The trial established court precedent in the New England colonies for how juries ruled on murder cases that involved the slave owner murdering an enslaved individual.
 The only documentation that she existed is several paragraphs in the Province and Court Records of Maine.
 She was called Rachel and lived in the town of Kittery in York County, Maine.
 Rachel was a slave, who was owned and beaten to death by Nathaniel Keen in late 1694 or early 1695.
The Type R ship is a United States Maritime Administration (MARAD) designation for World War II refrigerated cargo ship, also called a reefer ship.
 The R type ship was used in World War II, Korean War, Vietnam War and the Cold War.
 Type R ships were used to transport perishable commodities which require temperature-controlled transportation, such as fruit, meat, fish, vegetables, dairy products and other foods.
 The US Maritime Commission ordered 41 new refrigerated ships for the US Navy.
 Because of the difficulty of building refrigerated ships only two were delivered in 1944, and just 26 were delivered in 1945 and the remainder in 1946–48.
 The 41 R type ships were built in four groups.
 Two of design types were modified type C1 ships and two were modified type C2 ships.
 The United Fruit Company operated many of the R type ships in World War 2.
 The type R2-S-BV1 became the US Navy Alstede-class stores ship and the type R1-M-AV3 became the US Navy Adria-class stores ship.
Chris Bertram is a former Assistant Secretary for Budget and Programs, and Chief Financial Officer, for the United States Department of Transportation.
 As Assistant Secretary, he was responsible for the Department's budget, which totaled over $70 billion per year.
 He also oversaw the financial and performance management of the 12 agencies within the Department.
 Until August 2009, Bertram was a senior professional staff member with the Senate Committee on Commerce, Science, and Transportation.
 In that position, he was involved in developing legislation related to aviation, auto and highway safety, transportation security, pipelines, railroads, and fuel efficiency standards for automobiles.
 Prior to joining the Commerce Committee, Bertram was the Federal Aviation Administration's Assistant Administrator for Financial Services and Chief Financial Officer.
 He has also served as Staff Director for the House of Representative's United States House Transportation Subcommittee on Highways and Transit, and in various positions at the Office of Management and Budget.

Question: What type of transportation is involved in the paragraphs above?
Answer: Air