Epstein, R. L. (1979). Degrees of unsolvability: Structure and theory. Springer-Verlag.
Chicago-čujuhus (17. p.)Epstein, Richard L. Degrees of Unsolvability: Structure and Theory. Berlín: Springer-Verlag, 1979.
MLA-čujuhus (9. p.)Epstein, Richard L. Degrees of Unsolvability: Structure and Theory. Springer-Verlag, 1979.
Muitte dárkkistit čujuhemiid riektatvuođa, ovdal go geavahat daid iežat deavsttas.