Scheel, R. L. (1987). Introduction to the future. ETC Publications.
Chicago-čujuhus (17. p.)Scheel, Randall L. Introduction to the Future. Palm Springs, Calif.: ETC Publications, 1987.
MLA-čujuhus (9. p.)Scheel, Randall L. Introduction to the Future. ETC Publications, 1987.
Muitte dárkkistit čujuhemiid riektatvuođa, ovdal go geavahat daid iežat deavsttas.