@article{SF_1980__21_134431,
     author = {F. Pastijn and K.S.S. Nambooripad},
     title = {Subgroups of free idempotent generated regular semigroups.},
     journal = {Semigroup forum},
     pages = {1--8},
     publisher = {mathdoc},
     volume = {21},
     year = {1980},
     zbl = {0449.20061},
     url = {http://geodesic.mathdoc.fr/item/SF_1980__21_134431/}
}