I'm searching for three good definitions of technology in the economics literature, preferably by prominent economists: (a) one that matches the standard textbook approach that technology represents the production possibilities of factor substitution; (b) one that, in this way, sees nature as imposing technological constraints on production; and (c) one that sees technological progress as an augmentation of factor sustitution possibilities (as popularised by Solow, etc.). Even better would be if someone could point me towards the origins of any of these three (related) ideas. Many thanks in advance Adam McHugh