1. D.J. Skinner, Preliminary review of used lubricating oils in Canada, Envirornnent Canada, Economic and Technical Review, Rep. EPS 3-WP-74-4.
2. Final report of the task force on used oil disposal, API Publ. No. 4036.
3. E.W. Gagan, Air pollution emission and control technology — cement industry Environment Canada, Economic and Technical Review, Rep. EPS 3-AP-74-3.