1. Dokazatel'stvo suscestvovanijia n-znacnyh beskonecnyh asimmetricnyh posletovatel'nostei;Arshon;Mat. Sb.,1937
2. D. Bean, A. Ehrenfeucht and G. McNulty, Avoidable patterns in strings of symbols, to appear.
3. Les probabilités dénombrables et leurs applications arithmétiques;Borel;Rend. Circ. Mat. Palermo,1909
4. On non-repetitive sequences;Entringer;J. Combinatorial Theory, Ser. A.,1974