http://pubs.usgs.gov/pp/p1650-b/
http://biology.mcgill.ca/faculty/lechowicz/articles/JBI_Fang06.pdf
http://macroscope.world.coocan.jp/en/text/climveg/text.html
http://www.cedarcreek.umn.edu/biblio/fulltext/t1049.pdf
http://cct.or.cr/publicaciones/Life-Zone-Ecology.pdf
http://archive.org/details/waldbauaufnaturg00mayr
http://books.google.gr/books?id=vLhKts0_42YC&pg=PA29&lpg=PA29&dq=kira+warmth+index&source=bl&ots=6UQOXur2RB&sig=HyXgq394Ej-_OkQ81xHE8zeaolQ&hl=el&ei=uutdTra_JYegOuzW1cwC&sa=X&oi=book_result&ct=result&resnum=9&ved=0CGMQ6AEwCA#v=onepage&q=kira%20warmth%20index&f=false