cometadata/datacite-titles-descriptions-related-identifiers huggingface dataset:
DOI: 10.15468/dl.qhyeev
title: Occurrence Download

description: A dataset containing 10303 species occurrences available in GBIF matching the query:
{
 "and" : [
 "TaxonKey is Nyctalus noctula (Schreber, 1774)",
 "Geometry POLYGON((-29.179687 70.844672,-18.28125 28.921631,49.21875 29.535229,51.328125 71.635992,-29.179687 70.844672))",
 "HasGeospatialIssue is false",
 "HasCoordinate is true",
 "EventDate is greater than or equal to 1950-01-01"
 ]
}

 The dataset includes 10303 records from 124 constituent datasets; see https://api.gbif.org/v1/occurrence/download/0069732-160910150852091/datasets/export for details.
 
Data from some individual datasets included in this download may be licensed under less restrictive terms.
DOI: 10.25549/whit-c170-6206
title: Night views from Margarita Peak, Southern California, 1928

description: 3 photographs of night views from Margarita Peak, Southern California, 1928. "Subject: Nite[sic] views from Margarita Peak; Client: Calif[ornia] Botanic Garden; Number of Prints: 1 - ea[ch]; Size: 8x10; Finish: gl[ossy]; Year: 1928; Job: 2-16-58" -- on envelope.
DOI: 10.15468/dl.8amh9s
title: Occurrence Download

description: A dataset containing 11278 species occurrences available in GBIF matching the query:
{
 "and" : [
 "TaxonKey is Sorghum halepense (L.) Pers.",
 "HasGeospatialIssue is false",
 "HasCoordinate is true"
 ]
}

 The dataset includes 11278 records from 241 constituent datasets; see https://api.gbif.org/v1/occurrence/download/0069740-160910150852091/datasets/export for details.
 
Data from some individual datasets included in this download may be licensed under less restrictive terms.
DOI: 10.25549/whit-c170-30433
title: Mid-continent visitors, Southern California, 1930

description: 2 photographs of group of mid-continent visitors, Southern California, 1930. "Subject: Mid-continent investors; Agency: McCarty Co.; Client: Axelson; Original Print Order: 1 ea[ch]; Re-Order: 10 #1; Size: 8x10, 5x7; Finish: gl[ossy]; Year: 1930; Job: 12-10-60" -- on envelope front. "Operator's Report (Name): Dick; 2 Original Photographs - Size: 8x10; Amount: 5.00; 1 Exposures With Lights: globes, 1.00; Extra Charges: Cassidy" -- on envelope back.
DOI: 10.15468/dl.crdgvq
title: Occurrence Download

description: A dataset containing 76 species occurrences available in GBIF matching the query:
{
 "and" : [
 "TaxonKey is Fraxinus caroliniana Mill.",
 "HasGeospatialIssue is false",
 "HasCoordinate is true"
 ]
}

 The dataset includes 76 records from 17 constituent datasets; see https://api.gbif.org/v1/occurrence/download/0069743-160910150852091/datasets/export for details.
 
Data from some individual datasets included in this download may be licensed under less restrictive terms.
DOI: 10.25549/whit-c170-14914
title: General hospital, Metal Door and Trim Co., Los Angeles, CA, 1931

description: 8 photographs of hospital construction, Los Angeles, CA, 1931. "Subject: General Hospital; Client: Metal door and Trim Co., 157 arcade station; Original Print Order: 1 ea[ch]; Size: 8 1/2 x 11; Finish: linen; Year: 1931; Job: 3-25-156" -- on envelope front. "Name: Joe; 4 Original Photographs; 4 [Original Photographs - Size:] 8 1/2 x 11: 5.00; In City: 5.00; 2 Ounces of Flash Powder @0.85: 1.70; 11.70" -- on envelope back.
DOI: 10.15468/dl.8fxtbj
title: Occurrence Download

description: A dataset containing 65908 species occurrences available in GBIF matching the query:
{
 "and" : [
 "HasGeospatialIssue is false",
 "HasCoordinate is true",
 "DatasetKey is West African Vegetation Database"
 ]
}

 The dataset includes 65908 records from 1 constituent datasets; see https://api.gbif.org/v1/occurrence/download/0069747-160910150852091/datasets/export for details.
 
Data from some individual datasets included in this download may be licensed under less restrictive terms.
DOI: 10.25549/whit-c170-5896
title: View park, kids making movies, Southern California, 1928

description: 8 photographs of children, men and women, Southern California, 1928. "Subject: View park, kids makeing [sic] movies etc, H-2; Client: L.A. Investment; Number of Prints: 3 ea[ch]; Size: 8x10; Finish: gl[ossy]; Year: 1928; Job: 1-7-24" -- on envelope.
DOI: 10.15468/dl.igvpzi
title: Occurrence Download

description: A dataset containing 1874 species occurrences available in GBIF matching the query:
{
 "and" : [
 "TaxonKey is Fraxinus pennsylvanica Marshall",
 "HasGeospatialIssue is false",
 "HasCoordinate is true"
 ]
}

 The dataset includes 1874 records from 81 constituent datasets; see https://api.gbif.org/v1/occurrence/download/0069750-160910150852091/datasets/export for details.
 
Data from some individual datasets included in this download may be licensed under less restrictive terms.
DOI: 10.25549/whit-c170-5881
title: December 1927 blackboard, Southern California, 1928

description: Photograph of blackboard from December 1927, Southern California, 1928. "Subject: Dec[ember] 1927 blackboard; Client: W. Ross Campbell; Number of Prints: Three; Year: 1928; Job: 1-7-21" -- on envelope.
DOI: 10.25549/whit-c170-12899
title: Children and water bottle in studio, Southern California, 1929

description: 6 photographs of 2 children and water bottle in studio, Southern California, 1929. "Subject: Children & water bottle in studio; Agency: Western Lithograph Co., Mr. Hawthorne; Client: Mountain Spring Water Co.; Number of Prints: 1 ea[ch], 1 #3; Size: 8x10, 11x14; Finish: dull buff smooth 1/4 [inch] mar[gin], gl[ossy]; Mounted: mount; Year: 1929; Job: 8-22-131" -- on envelope.
DOI: 10.15468/dl.cdoy9z
title: Occurrence Download

description: A dataset containing 50975 species occurrences available in GBIF matching the query:
{
 "and" : [
 "TaxonKey is Quercus pubescens Willd.",
 "Geometry POLYGON((-37.18 21.04,-37.18 67.17,73.04 67.17,73.04 21.04,-37.18 21.04))",
 "HasGeospatialIssue is false",
 "BasisOfRecord is Human Observation"
 ]
}

 The dataset includes 50975 records from 48 constituent datasets; see https://api.gbif.org/v1/occurrence/download/0069751-160910150852091/datasets/export for details.
 
Data from some individual datasets included in this download may be licensed under less restrictive terms.
DOI: 10.25549/whit-c170-30328
title: Intersection of Willow Street & American Avenue [Long Beach Boulevard], Long Beach, CA, 1930

description: 5 photographs of intersection of Willow Street & American Avenue [Long Beach Boulevard], Long Beach, CA, 1930. "Subject: intersection of Willow & American Ave[nue], Long Beach; Client: Associated Indemnity; Year: 1930; Job: 11-12-64" -- on envelope front. "Operator's Report: Joe; Original Photographs: 5 8x10; Amount: 5.00, 2.80, 4.00; Hours: 2 @ 2.00; Extra CHarges: Kellog" -- on envelope back.
DOI: 10.15468/dl.kajn9y
title: Occurrence Download

description: A dataset containing 1509 species occurrences available in GBIF matching the query:
{
 "and" : [
 "TaxonKey is Pamphagidae",
 "DatasetKey is Pamphagidae (Orthoptera: Acridoidea) from the Palaearctic Region: taxonomy, classification, keys to genera and a review of the tribe Nocarodeini I. Bolívar"
 ]
}

 The dataset includes 1509 records from 1 constituent datasets; see https://api.gbif.org/v1/occurrence/download/0069752-160910150852091/datasets/export for details.
 
Data from some individual datasets included in this download may be licensed under less restrictive terms.
DOI: 10.25549/whit-c170-12834
title: Small radio, Southern California, 1929

description: 2 photographs of small radio, Southern California, 1929. "Subject: Small radio; Agency: Graham; Client: Master Radio Dist. Co., Mr. Davidson, 1682 W[est] 35th Pl[ace]; Number of Prints: 1 ea[ch]; Size: 8x10; Finish: gl[ossy]; Year: 1929; Job: 8-20-119" -- on envelope.
DOI: 10.25549/whit-c170-5935
title: George Washington School, Southern California, 1928

description: 7 photographs of exterior of George Washington High School, Southern California, 1928. "Subject: George Washington School; Agency: Phillip Meaney; Client: Simmons brick Co.; Classifications: B School; Number of prints: 1-ea[ch], off 3; Year: 1928; Job: 1-20-77" -- on envelope.
DOI: 10.25549/whit-c170-15231
title: Intersection at East Washington Boulevard and Griffith Avenue, Los Angeles, CA, 1931

description: 4 photographs of roads, East Washington Boulevard and Griffith Avenue, Los Angeles, CA, 1931. "Subject: Intersection, Washington and Griffith; Client: Union Indemnity Co.; Original Print Order: 3 ea[ch]; Size: 8x10; Finish: gl[ossy]; Year: 1931; Job: 4-3-17" -- on envelope front. "Name: Joe; 4 Original Photographs - Size: 8x10; In City: 4.00" -- on envelope back.
DOI: 10.15468/dl.qy92nx
title: Occurrence Download

description: A dataset containing 0 species occurrences available in GBIF matching the query:
{
 "GenusKey" : [
 "is Eugenia"
 ]
}

 The dataset includes 0 records from 0 constituent datasets; see https://api.gbif.org/v1/occurrence/download/0007167-240506114902167/datasets/export for details.
DOI: 10.15468/dl.rvrv2c
title: Occurrence Download

description: A dataset containing 16857 species occurrences available in GBIF matching the query:
{
 "TaxonKey" : [
 "is Larix kaempferi (Lamb.) Carrière"
 ]
}

 The dataset includes 16857 records from 369 constituent datasets; see https://api.gbif.org/v1/occurrence/download/0007166-240506114902167/datasets/export for details.
 
Data from some individual datasets included in this download may be licensed under less restrictive terms.
DOI: 10.25549/whit-c170-84567
title: RPM visomatic lecture, Southern California, 1936

description: 39 photographs of RPM visomatic lecture, Southern California, 1936. "Subject: RPM. Visomatic Lecture; Agency: Rodney Gilliam; Client: Standard Oil Co[mpany]; Classifications: see 8x10 neg[ative]s, H-men models-S-act shot; Original Print Order: 1 ea[ch]; Size: 6 3/4x9; Finish: gl[ossy]; Mount: see Harry; Job: 63-31-213A; Year: 1936" -- on envelope front. "Operator's Report Name: Dick; 26 Original Photographs-At Studio 9x6 3/4 m[oun]t[e]d, models act, work etc[etera] [ilg], 6 Original Photographs-Size #50-51, 52, 53, 55, 56, 1 Original Photograph-Size #128A with model, 1 Original Photograph-Size #105 with models, Rental of uniforms, original photo chrysler dark, composit & extra ret[ilg], moody, decal, #15 and #131; Amount: $1025, 22.50, 10.00, 20.00, 12.[ilg], 3.[ilg], 19.50" -- on envelope back.
DOI: 10.15468/dl.wessrh
title: Occurrence Download

description: A dataset containing 28 species occurrences available in GBIF matching the query:
{
 "and" : [
 "TaxonKey is Pithecoctenium crucigerum (L.) A.H.Gentry",
 "Geometry POLYGON((-90.52 19.59,-90.52 21.64,-87.08 21.64,-87.08 19.59,-90.52 19.59))",
 "HasGeospatialIssue is false"
 ]
}

 The dataset includes 28 records from 8 constituent datasets; see https://api.gbif.org/v1/occurrence/download/0069755-160910150852091/datasets/export for details.
 
Data from some individual datasets included in this download may be licensed under less restrictive terms.
DOI: 10.25549/whit-c170-58097
title: Tournament of Roses, Pasadena, CA, 1933

description: 20 photographs of floats at Tournament of Roses, Pasadena, CA, 1933. "Client: Tournament of Roses; Classifications: F - parades; Re-Order: 1 #26, 1 #56; Size: 11x14 1/4 in, 11x14; Finish: border, 1/4" margin; Mount: D.W. opal g. vitavia paper, horizontal opal G; Job: 1-1-5-B; Year: 1933" -- on envelope front. "Original Photographs-Size: charged on A" -- on envelope back.
DOI: 10.15468/dl.bteeap
title: Occurrence Download

description: A dataset containing 47 species occurrences available in GBIF matching the query:
{
 "TaxonKey" : [
 "is Panthera uncia (Schreber, 1775)"
 ]
}

 The dataset includes 47 records from 14 constituent datasets; see https://api.gbif.org/v1/occurrence/download/0069758-160910150852091/datasets/export for details.
 
Data from some individual datasets included in this download may be licensed under less restrictive terms.
DOI: 10.25549/whit-c170-97819
title: Dick Whittington Photography Collection, 1924-1987
DOI: 10.15468/dl.wdojki
title: Occurrence Download

description: A dataset containing 3369 species occurrences available in GBIF matching the query:
{
 "TaxonKey" : [
 "is Euterpe oleracea Mart."
 ]
}

 The dataset includes 3369 records from 59 constituent datasets; see https://api.gbif.org/v1/occurrence/download/0069760-160910150852091/datasets/export for details.
 
Data from some individual datasets included in this download may be licensed under less restrictive terms.
DOI: 10.25549/whit-c170-4558
title: 1370 North Irving Avenue, Glendale, CA, 1925

description: Photograph of exterior of 1370 North Irving Avenue, Glendale, CA, 1925. "Subject: 1370 No[rth] Irwing Ave[nue], Glendale; Client: W. Dwight Hammond; Year: 1925; Job: 9-5-14" -- on envelope.
DOI: 10.25549/whit-c170-83778
title: Granada Hills publicity, Los Angeles, CA, 1936

description: 11 photographs of Granada Hills publicity, Los Angeles, CA, 1936. "Subject: Granada publicity; Client: California Bank; Classifications D-trees I-orchards; Original Print Order: 1 ea[ch]; Size: 8x10, 5x7; Finish: gl[ossy]; [ilg] Wright; Re-order: 1#2; Job: 5-15-104; Year: 1936" -- on envelope front. "Operator's Report Name: Dean; 11 Original Photographs--Size: 8x10; 60 Miles: Transportation at 7¢; 6 Hours: Time @ 2.00; Model (Name): Kay Hughes; Amount: 16.50, 4.20, 12.00, 10.00; Extra Charges: Geo[rge] Stiller" -- on envelope back.
DOI: 10.15468/dl.yoabhd
title: Occurrence Download

description: A dataset containing 41396 species occurrences available in GBIF matching the query:
{
 "and" : [
 "TaxonKey is Rattus rattus (Linnaeus, 1758)",
 "HasGeospatialIssue is false"
 ]
}

 The dataset includes 41396 records from 207 constituent datasets; see https://api.gbif.org/v1/occurrence/download/0069762-160910150852091/datasets/export for details.
 
Data from some individual datasets included in this download may be licensed under less restrictive terms.
DOI: 10.25549/whit-c170-2442
title: Goodyear protectors, Oil Well Equipment Co., Southern California, 1931

description: 2 photographs of Goodyear protectors, Oil Well Equipment Co., Southern California, 1931. "Subject: Goodyear protectors; Agency: McCarty; Client: Oil Well Equipment Co.; Original print order: 1 ea[ch]; Size: 8x10, 5x7; Finish: gl[ossy]; Year: 1931; Job: 11-28-180" -- on envelope front. "Extra charges: #4380 A; Original photographs-At Studio: 2, 8x10, Special Lighting or Background, 4.00; Operator's report (Name): Joe" -- on envelope back.
DOI: 10.15468/dl.kuc9q7
title: Occurrence Download

description: A dataset containing 45 species occurrences available in GBIF matching the query:
{
 "and" : [
 "TaxonKey is Ceiba schottii Britten & Baker fil.",
 "Geometry POLYGON((-90.15 20.38,-90.15 21.40,-88.43 21.40,-88.43 20.38,-90.15 20.38))",
 "HasGeospatialIssue is false"
 ]
}

 The dataset includes 45 records from 11 constituent datasets; see https://api.gbif.org/v1/occurrence/download/0069763-160910150852091/datasets/export for details.
 
Data from some individual datasets included in this download may be licensed under less restrictive terms.
DOI: 10.25549/whit-c170-57966
title: Intersection of East Washington Boulevard & South Central Avenue, Los Angeles, CA, 1935

description: 3 photographs of intersection of East Washington Boulevard & South Central Avenue, Los Angeles, CA, 1935. "Subject: Intersection of Washington & Central; Client: Bordens Farm Products Co., Noel, 915 No[rth] Mansfield; Original Print Order: 1 ea[ch]; Size: 8x10; Finish: gl[ossy]; Year: 1935; Job: 1-29-164" -- on envelope front. "Operator's Report Name: Dean; 3 Original Photographs-Size: 8x10 ext[erior]; Amount: 6.00; Extra Charges: order #1510" -- on envelope back.
DOI: 10.25549/whit-c170-83773
title: Granada Hills publicity, Los Angeles, CA, 1936

description: 11 photographs of Granada Hills publicity, Los Angeles, CA, 1936. "Subject: Granada publicity; Client: California Bank; Classifications D-trees I-orchards; Original Print Order: 1 ea[ch]; Size: 8x10, 5x7; Finish: gl[ossy]; [ilg] Wright; Re-order: 1#2; Job: 5-15-104; Year: 1936" -- on envelope front. "Operator's Report Name: Dean; 11 Original Photographs--Size: 8x10; 60 Miles: Transportation at 7¢; 6 Hours: Time @ 2.00; Model (Name): Kay Hughes; Amount: 16.50, 4.20, 12.00, 10.00; Extra Charges: Geo[rge] Stiller" -- on envelope back.
DOI: 10.15468/dl.fdp2xo
title: Occurrence Download

description: A dataset containing 2886 species occurrences available in GBIF matching the query:
{
 "and" : [
 "TaxonKey is Eubucco bourcierii (Lafresnaye, 1845)",
 "Country is Colombia"
 ]
}

 The dataset includes 2886 records from 48 constituent datasets; see https://api.gbif.org/v1/occurrence/download/0069766-160910150852091/datasets/export for details.
 
Data from some individual datasets included in this download may be licensed under less restrictive terms.
DOI: 10.25549/whit-c170-57991
title: Program committee, women Vaudeville players, Los Angeles, CA, 1935

description: 2 photographs of a group of women looking at a The Vaudeville Players program, Los Angeles, CA, 1935. "Subject: Program Committee, women Vaudeville Players; Client: Ambassador Hotel; Original print order: 1 ea[ch]; Size: 8x10; Finish: gl[ossy]; Year: 1935; Job: 2-6-27" -- on envelope front. "Extra charges: John Brown; Original photographs-Size: 2, 8x10, In City, 5.50; Operator's report (Name): Joe" -- on envelope back.
DOI: 10.15468/dl.ymniua
title: Occurrence Download

description: A dataset containing 26896 species occurrences available in GBIF matching the query:
{
 "TaxonKey" : [
 "is Linepithema humile (Mayr, 1868)"
 ]
}

 The dataset includes 26896 records from 38 constituent datasets; see https://api.gbif.org/v1/occurrence/download/0069767-160910150852091/datasets/export for details.
 
Data from some individual datasets included in this download may be licensed under less restrictive terms.
DOI: 10.25549/whit-c170-5204
title: May Festival, Broadway Department Store, Los Angeles, CA, 1925

description: 4 photographs of May Festival, Broadway Department Store, Los Angeles, CA, 1925. "Subject: May Festival, (see also 7x17); Client: Broadway Dep[artmen]t Store; Year: 1925; Job: 55-10-24" -- on envelope.
DOI: 10.15468/dl.cdiarz
title: Occurrence Download

description: A dataset containing 4 species occurrences available in GBIF matching the query:
{
 "TaxonKey" : [
 "is Leandra tristis Cogn."
 ]
}

 The dataset includes 4 records from 3 constituent datasets; see https://api.gbif.org/v1/occurrence/download/0069768-160910150852091/datasets/export for details.
 
Data from some individual datasets included in this download may be licensed under less restrictive terms.
DOI: 10.25549/whit-c170-58101
title: Tournament of Roses, Pasadena, CA, 1933

description: 20 photographs of floats at Tournament of Roses, Pasadena, CA, 1933. "Client: Tournament of Roses; Classifications: F - parades; Re-Order: 1 #26, 1 #56; Size: 11x14 1/4 in, 11x14; Finish: border, 1/4" margin; Mount: D.W. opal g. vitavia paper, horizontal opal G; Job: 1-1-5-B; Year: 1933" -- on envelope front. "Original Photographs-Size: charged on A" -- on envelope back.
DOI: 10.25549/whit-c170-59688
title: Madden & Grant lubricating service, Pennzoil, Southern California, 1933

description: 2 photographs of service station and men working on cars, Southern California, 1933. "Subject: Madden & Grant Lubricating service; Client: Pennzoil; Original Print Order: 1 ea[ch]; Size: 8x10; Finish: gl[ossy]; Year: 1933; Job: 1-11-37" -- on envelope front. "Operator's Report Name: Joe; 2--8x10; Amount: 4.50" -- on envelope back.
DOI: 10.5281/zenodo.10843481
title: Quality assessment of biomass pellets available on the market: Example from Poland

description: Submitted data was used to write an article: Drobniak, A., Jelonek, Z., Mastalerz, M., Jelonek, I., Widziewicz-Rzońca, K., Quality assessment of biomass pellets available on the market: Example from Poland. Environmental Science and Pollution Research. https://doi.org/10.1007/s11356-024-33452-1

 

Funding acknowledgments: The project is co-financed by the Polish National Agency for Academic Exchange within the Polish Returns Programme (BPN/PPO/2021/1/00005/DEC/1), the National Science Center, Poland (2022/01/1/ST10/00024), and the research activities co-financed by the funds granted under the Research Excellence Initiative of the University of Silesia in Katowice, Poland. 

 

Article Abstract: This study evaluates the quality of 30 biomass pellets sold for residential use in Poland. It provides data on their physical, chemical, and petrographic properties and compares them to existing standards and the information provided by the fuel producers. The results reveal considerable variations in the quality of the pellets and show that some of the purchased samples are not within the DINplus and/or ENplus certification thresholds. Among all 30 purchased samples, only one passes the quality thresholds set by the PL-US BIO, a newly established quality certification in Poland that combines quality assessment following DINplus with optical microscopy analysis. The primary issues causing a decrease in pellet quality include elevated ash and fines content, compromised mechanical durability, too low ash melting temperature, and additions of undesired additions like bark, inorganic matter, and petroleum products. Our research highlights the need for improved fuel quality control measures, and transparent and accurate product labeling, as well as the need for a comprehensive and publicly available national database of solid biomass fuel producers and fuels sold. These are essential steps toward increasing customers’ awareness and trust, encouraging them to embrace biomass fuels as reliable and sustainable sources of energy.
DOI: 10.5281/zenodo.10843482
title: Quality assessment of biomass pellets available on the market: Example from Poland

description: Submitted data was used to write an article: Drobniak, A., Jelonek, Z., Mastalerz, M., Jelonek, I., Widziewicz-Rzońca, K., Quality assessment of biomass pellets available on the market: Example from Poland. Environmental Science and Pollution Research. https://doi.org/10.1007/s11356-024-33452-1

 

Funding acknowledgments: The project is co-financed by the Polish National Agency for Academic Exchange within the Polish Returns Programme (BPN/PPO/2021/1/00005/DEC/1), the National Science Center, Poland (2022/01/1/ST10/00024), and the research activities co-financed by the funds granted under the Research Excellence Initiative of the University of Silesia in Katowice, Poland. 

 

Article Abstract: This study evaluates the quality of 30 biomass pellets sold for residential use in Poland. It provides data on their physical, chemical, and petrographic properties and compares them to existing standards and the information provided by the fuel producers. The results reveal considerable variations in the quality of the pellets and show that some of the purchased samples are not within the DINplus and/or ENplus certification thresholds. Among all 30 purchased samples, only one passes the quality thresholds set by the PL-US BIO, a newly established quality certification in Poland that combines quality assessment following DINplus with optical microscopy analysis. The primary issues causing a decrease in pellet quality include elevated ash and fines content, compromised mechanical durability, too low ash melting temperature, and additions of undesired additions like bark, inorganic matter, and petroleum products. Our research highlights the need for improved fuel quality control measures, and transparent and accurate product labeling, as well as the need for a comprehensive and publicly available national database of solid biomass fuel producers and fuels sold. These are essential steps toward increasing customers’ awareness and trust, encouraging them to embrace biomass fuels as reliable and sustainable sources of energy.