Columbia subject headings:
Athabasca Tar Sands (Alta.)--History.
Chemists--Canada--Correspondence.
Clark, Karl A. (Karl Adolph), 1888-1966.
Oil sands industry--Alberta--History.
Harvard subject headings:
Clark, Karl A. (Karl Adolph), 1888-1966--Correspondence.
Oil sands extraction plants--Alberta.
Oil sands--Alberta--Fort McMurray Region.
Petroleum engineers--Alberta--Correspondence.
Princeton subject headings:
Athabasca Tar Sands (Alta.)--History.
Chemists--Canada--Correspondence.
Clark, Karl A. (Karl Adolph), 1888-1966.
Oil sands industry--Alberta--History.