@article{10_4153_CJM_1990_058_9,
     author = {Margolis, S. W. and Meakin, J. C. and Stephen, J. B.},
     title = {Free {Objects} in {Certain} {Varieties} of {Inverse} {Semigroups}},
     journal = {Canadian journal of mathematics},
     pages = {1084--1097},
     year = {1990},
     volume = {42},
     number = {6},
     doi = {10.4153/CJM-1990-058-9},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CJM-1990-058-9/}
}