[1] Anderson F., Fuller K., Rings and categories of modules, Springer-Verlag, New York-Heidelberg, 1974
[2] Bulman-Fleming S., Mahmoudi M., The category of S-posets, Semigroup Forum, 2005, 71, 443–461 http://dx.doi.org/10.1007/s00233-005-0540-y
[3] Kilp M., Knauer U., Mikhalev A., Monoids acts and categories, Walter de Gruyter, Berlin, 2000
[4] Shi X., Liu Z., Wang F., Bulman-Fleming S., Indecomposable projective and flat S-posets, Comm. Algebra, 2005, 33, 235–251 http://dx.doi.org/10.1081/AGB-200040992