[1] Čech E.: Topological spaces. Аcademia, Pгague 1966.
[2] Pickett H. E.: 
Homomorphisms and subalgebras of multialgebras. Pacific J. Math. 21 (1967), 327-342. 
MR 0213278 | 
Zbl 0149.26101 
[3] Rabin M. O., Scott D.: 
Finite automata and their decision problems. IBM Jouгnal 3 (1959), 114-125. 
MR 0103795 
[4] Schmidt J.: 
Algebraic operations and algebraic independence in algebras with infinitary operations. Math. Jap. VI, 77-112. 
MR 0156810 | 
Zbl 0119.25903