Current knowledge on the origin and structure of Estonian kukersite kerogenLille, ÜloOil shale2003 / 3, p. 253-263 : ill Current knowledge on the origin and structure of Estonian kukersite kerogenLille, ÜloAbstracts : Symposium on Oil Shale 2002, 18-21 November 2002, Tallinn, Estonia2002 / p. 26