1. Real commutative semigroups on the plane;Horne, J. G., Jr.;Pacific J. Math.,1961
2. One-parameter subgroups in semigroups in the plane;Horne, J. G., Jr.;Michigan Math. J.,1962
3. On a class of semigroups on 𝐸_{𝑛};Mostert, Paul S.;Proc. Amer. Math. Soc.,1956
4. Semigroups with identity on a manifold;Mostert, Paul S.;Trans. Amer. Math. Soc.,1959
5. Plane semigroups;Mostert, Paul S.;Trans. Amer. Math. Soc.,1962