[1] Jiang Luh.:
On the Concepts of Radical of Semigroup Having Kernel. Portugaliae Mathematica, 19 (1960), 189-198.
MR 0131482 |
Zbl 0095.01405
[2] Ляпин E. C.: Пoлyгpynnы. Гocyдapcтвeннoe издaтeльcтвo физикo-мaтeмaтичecкoй литepaтypы, Mocквa 1960.
[3] Morse M., Hedlund G. A.:
Symbolic Dynamics. American Journal of Mathematics, 60 (1938), 815-866.
MR 1507944 |
Zbl 0019.33502