A. N. Dëgtev2026-03-222026-03-22198210.1016/s0049-237x(09)70194-6https://doi.org/10.1016/s0049-237x(09)70194-6https://andeanlibrary.org/handle/123456789/83508enDegree (music)SemilatticeMathematicsRecursively enumerable languageComputability theoryRecursion (computer science)Discrete mathematicsCombinatoricsSmall Degrees in Ordinary Recursion Theorybook-chapter