@article{10_1017_S0017089500009435,
     author = {Blyth, T. S. and Pinto, G. A.},
     title = {Principally ordered regular semigroups},
     journal = {Glasgow mathematical journal},
     pages = {349--364},
     year = {1990},
     volume = {32},
     number = {3},
     doi = {10.1017/S0017089500009435},
     url = {http://geodesic.mathdoc.fr/articles/10.1017/S0017089500009435/}
}