"In practically all parts of the world large deposits of bituminous shales can be found. Due to their oil-yield , they have often been looked upon with considerable interest, but their rather low value as fuel - including normally a gain of 4 - 10% of oil - has hitherto made their exploitation unattractible. To develop a process where you may gain a few percent of oil and have up to 90 percent left as waste, is of course no tempting job."