http://www.erowid.org/library/books_online/pihkal/pihkal109.shtml (http://www.erowid.org/library/books_online/pihkal/pihkal109.shtml)
https://www.thevespiary.org/rhodium/Rhodium/djvu/tlc.zubrick5.djvu (https://www.thevespiary.org/rhodium/Rhodium/djvu/tlc.zubrick5.djvu)
http://www.lizardtech.com/products/index.php?x=2&p=1&o=1 (http://www.lizardtech.com/products/index.php?x=2&p=1&o=1)