[1] BIGARD A.:
Contribution à la théorie des groupes гéticulés. These Fac. Sci. Paгis, 1969.
MR 0250950
[2] RACHŮNEK J.:
Directed convex subgгoups of ordered groups. Acta Univ. Palack. Olomucensis, Fac. Reг. Nat., 41, 1973, 39-46.
MR 0357273
[3] RACHŮNEK J.:
Prime subgroups of oгdered groups. Czechoslov. Math. J., 24 (99), 1974, 541-551.
MR 0357274