2 Kotarba M J. Isotopic geochemistry and habitat of the natural gases from the Upper Carboniferous Zacier coal-bearing Formation in theNowa Ruda coal district (Lower Silesia, Poland). Org Geochem, 1990, 16: 549-560？？
[2]
3 Liu D M, Yang Q, Tang D Z. Reaction kinetics of coalification in Ordos Basin, China. In: Yang Q, ed. Geology of Fossil Fuel-coal.Utrecht: The Netherlands, 1997. 147-159
5 Kotarba M J, Rice D D. Composition and origin of coalbed gases in the Lower Silesian basin, southwest Poland. Appl Geochem, 2001, 16:895-910？？
[5]
8 Raymond M, Landais P. Artificial coalification: Comparison of confined pyrolysis and hydrous pyrolysis. Fuel, 1994, 73: 1691-1696？？
[6]
10 Cramer B. Methane generation from coal during open system pyrolysis investigate by isotope specific, Gaussian distributed reaction kinetics.Org Geochem, 2004, 35: 379-392？？
[7]
13 Liu Q Y, Liu W H, Dai J X. Characterization of pyrolysates from maceral components of Tarim coals in closed system experiments andimplications to natural gas generation. Org Geochem, 2007, 38: 921-934？？
17 Yao S, Xue C, Hu W, et al. A comparative study of experimental maturation of peat, brown coal and subbituminous coal: Implications forcoalification. Int J Coal Geol, 2006, 66: 108-118？？
[10]
20 Stach E, Mackowsky M-Th, Teichmüller M, et al. Stach’s Textbook of Coal Petrology. 2nd ed. Berlin: Gebrüder Borntraeger, 1982
[11]
1 Clayton J L. Geochemistry of coalbed gas―A review. Int J Coal Geol, 1998, 35: 159-173？？
7 Landais P. Assessement of coal potential evolution by experimental simulation of natural coalification. Org Geochem, 1991, 17: 705-710？？
[14]
9 Behar F, Vandenbroucke M, Teermann S C, et al. Experimental simulation of gas generation from coals and a marine kerogen. ChemGeol, 1995, 126: 247-260
15 Behar F, Vandenbroucke M, Teerman S C, et al. Experimental simulation of gas generation from coals and a marine kerogen. Chem Geol,1995, 126: 247-260？？
18 Rollins M S, Cohen A D, Bailey A M, et al. Organic chemical and petrographic changes induced by early-stage artificial coalification ofpeats. Org Geochem, 1991, 17: 451-465？？
[20]
19 Kracht O, Gleixner G. Isotope analysis of pyrolysis products from Sphagnum peat and dissolved organic matter from bog water. OrgGeochem, 2000, 31: 645-654
[21]
21 Stahl J W, Carey B D. Source-rock identification by isotope analyses of natural gases from fields in the Val Verde and Delaware Basins,West Texas. Chem Geol, 1975, 16: 257-267？？
