Low temperature pyrolysis of graptolite argillite (Dictyonema shale) in autoclavesŠarajeva, Galina; Tiikma, Laine; Luik, Hans; Johannes, IlleInternational journal of engineering research and applications2015 / p. 16-22 : ill http://www.ijera.com/papers/Vol5_issue11/Part%20-%201/D511011622.pdf