A method for recovery of heat generated by the combustion of coal in situ within coal seams in the earth. Three embodiments are described: one, in which the coal seam crops out and into which can be drilled and inserted a pipe, through the coal seam, to a central point, where it is joined with a vertical...http://www.google.de/patents/US4089373?utm_source=gb-gplus-sharePatent US4089373 - Situ coal combustion heat recovery method
