//-->
Puti razvitija toplivnogo chozjajstva Vostočnoj Sibiri
Probst, Abram E., (1960)
A comparison between the petrography of south african and some other palaeozoic coals
Snyman, C. P., (1961)
El problema de los combustibles minerales solidos en la Argentina
Abrines, Maria Delia, (1948)