@article{SF_1989__39_2_134987,
     author = {E.E. DeVun and G. Graham},
     title = {Semigroups with commuting threads.},
     journal = {Semigroup forum},
     pages = {203--214},
     publisher = {mathdoc},
     volume = {39},
     number = {2},
     year = {1989},
     zbl = {0672.22007},
     url = {http://geodesic.mathdoc.fr/item/SF_1989__39_2_134987/}
}