Purga, Jaanus (2004). "Today's rainbow ends in Fushun"(PDF). Oil Shale. A Scientific-Technical Journal. 21 (4). Estonian Academy Publishers: 269–272. ISSN0208-189X. Retrieved 2009-02-14.
Alali, Jamal; Abu Salah, Abdelfattah; Yasin, Suha M.; Al Omari, Wasfi (2006). "Oil Shale in Jordan"(PDF). Natural Resources Authority of Jordan. Retrieved 2009-02-17.[permanent dead link]
Purga, Jaanus (2004). "Today's rainbow ends in Fushun"(PDF). Oil Shale. A Scientific-Technical Journal. 21 (4). Estonian Academy Publishers: 269–272. ISSN0208-189X. Retrieved 2009-02-14.