[2] Misra B K. International Journal of Coal Geology, 1992, 20: 145.

[3] Teerman S C, Crelling J C. Aapg Bulletin-American Association of Petroleum Geologists, 1984, 68(7): 951.

[4] Langenheim J H. Science, 1969, 163(3872): 1157.

[5] Lin R, Davis A. Organic Geochemitry, 1988, 12(4): 363

[6] Crelling J C. Journal of Microscopy, 1983, 132(3): 251.

[7] Crelling J C, Pugmire R J, Meuzelaar H, et al. Energy & Fuels, 1991, 5(5): 688.

[8] Gijzel P V. Review of Palaeobotany & Palynology, 1967, 2(1-4): 49.

[9] Teerman S C, Crelling J C, Glass G B. International Journal of Coal Geology, 1987, 7(4): 315.

[12] Matuszewska A, Czaja M. Talanta, 2002, 56(6): 1049.

[13] Kool J, Poole I, Bergen P F V. Organic Geochemistry, 2009, 40(6): 700.

[14] Brunsman M J, Kneller W A. Society for Organic Petrology, 1985, 2: 24.