Energy : from fossil fuels to sustainable energy resources / authors Jürgen Salay ... [et al.] . Uppsala :  Uppsala University , 1997 . 52 s . ISBN 91-7005-125-9
http://www2.balticuniv.uu.se/bup-3/index.php/public/textbooks-course-materials/course-materials/a-sustainable-baltic-region/20-a-sustainable-baltic-region-session-2/file . [2, z toho požičaných 0]