1. A. J. Czerniakiewicz, “Automorphisms of a free associative algebra of rank 2. I,” Trans. Am. Math. Soc., 160, 393-401 (1971).
2. A. J. Czerniakiewicz, “Automorphisms of a free associative algebra of rank 2. II,” Trans. Am. Math. Soc., 171, 309-315 (1972).
3. H. W. Jung, “Uber ganze birationale Transformationen der Ebene,” J. Reine Angew. Math., 184, 161-174 (1942).
4. W. van der Kulk, “On polynomial rings in two variables,” Nieuw Arch. Wiskd., III. Ser., 1, 33-41 (1953).
5. L. G. Makar-Limanov, “Automorphisms of a free algebra with two generators,” Funkts. Anal. Prilozh., 4, 107/108 (1970).