@article{SF_1974__7_134000,
     author = {G.B. Preston},
     title = {Clifford, {A.H.} - {An} appreciation of his his work on the occasion of his sixty-fifth birthday.},
     journal = {Semigroup forum},
     pages = {32--57},
     publisher = {mathdoc},
     volume = {7},
     year = {1974},
     zbl = {0275.01014},
     url = {http://geodesic.mathdoc.fr/item/SF_1974__7_134000/}
}