@article{10_1017_S0017089500030986,
     author = {Pastijn, Francis and Yan, Xiaoying},
     title = {Semigroup varieties closed for the {Bruck} extension},
     journal = {Glasgow mathematical journal},
     pages = {371--380},
     year = {1994},
     volume = {36},
     number = {3},
     doi = {10.1017/S0017089500030986},
     url = {http://geodesic.mathdoc.fr/articles/10.1017/S0017089500030986/}
}