@article{10_21136_CMJ_1979_101581,
     author = {Lopez, Antonio M., Jr. and Luedeman, John K.},
     title = {Quasi-injective $S$-systems and their $S$-endomorphism semigroup},
     journal = {Czechoslovak Mathematical Journal},
     pages = {97--104},
     year = {1979},
     volume = {29},
     number = {1},
     doi = {10.21136/CMJ.1979.101581},
     mrnumber = {518143},
     zbl = {0445.20039},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.21136/CMJ.1979.101581/}
}