[1] JASEM M.: Weak isometries and direct decompositions of dually residuated lattice ordered semigroups. Math. Slovaca 43 (1993), 119-136. MR 1274597 | Zbl 0782.06012

[2] KOVÁŘ T.: Any $DR\ell$-semigroup is the direct product of a commutative $\ell$-group and a $DR\ell$-semigroup with the least element. Discuss. Math. Algebra Stochastic Methods 16 (1996), 99-105. MR 1429801

[3] KOVÁŘ T.: Note on axioms of a dually residuated lattice ordered semigroup. Discuss. Math. Algebra Stochastic Methods 17 (1997), 89-90. MR 1633244 | Zbl 0906.06012

[4] KOVÁŘ T.: Two remarks on dually residuated lattice ordered semigroups. Math. Slovaca 49 (1999), 17-18. MR 1804468 | Zbl 0943.06007

[5] SWAMY K. L. N.: Dually residuated lattice ordered semigroups. Math. Ann. 159 (1965), 105-114. MR 0183797 | Zbl 0138.02104

[6] SWAMY K. L. N.: Dually residuated lattice ordered semigroups II. Math. Ann. 160 (1965), 64-71. MR 0191851 | Zbl 0138.02104

[7] SWAMY K. L. N.: Dually residuated lattice ordered semigroups III. Math. Ann. 167 (1966), 71-74. MR 0200364 | Zbl 0158.02601