@article{AM2_1977__15_136628,
     author = {S.R. Caradus},
     title = {An equational approach to products of relatively regular operators.},
     journal = {Aequationes mathematicae},
     pages = {55--62},
     year = {1977},
     volume = {15},
     zbl = {0348.47010},
     url = {http://geodesic.mathdoc.fr/item/AM2_1977__15_136628/}
}