"shale coal" . . . . . . . . . . "Shale Mine" . . "Oil shale" . . . "kerosene shale" . . "oil shale" . . . "oil shales" . . . . . . "shale" . "shale plays" . "oil-shale" . . . "Oil shale" . . "oil shale mining" . "Oil from Shale" . . . "oil" . "shale oil" .