[1] Š. Černák: 
Lexicographic products of cyclically ordered groups. Math. Slovaca 45 (1995), 29–38. 
MR 1335837[3] J. Jakubík: 
Lexicographic products of partially ordered groupoids. Czechoslovak Math. J. 14 (1964), 281–305. (Russian) 
MR 0167558[4] J. Jakubík: 
On extended cyclic orders. Czechoslovak Math. J. 44 (1994), 661–675. 
MR 1295142[5] A. J. Malcev: 
On ordered groups. Izv. Akad. nauk SSSR, ser. math. 13 (1949), 473–482. (Russian) 
MR 0032645[6] V. Novák, M. Novotný: 
Universal cyclically ordered sets. Czechoslovak Math. J. 35 (1985), 158–161. 
MR 0779343[7] V. Novák, M. Novotný: 
On representation of cyclically ordered sets. Czechoslovak Math. J. 39 (1989), 127–132. 
MR 0983489[8] L. Rieger: 
On ordered and cyclically ordered groups, I, II, III. Věstník král. české spol. nauk (1946), 1–31. 
MR 0020995