Regular Expressions: New Results and Open Problems. - Keith Ellul; Jeffrey O. Shallit; Ming-wei Wang (DCFS, 2002)

Non-uniqueness and radius of cyclic unary NFAs. - Michael Domaratzki; Keith Ellul; Jeffrey O. Shallit; Ming-wei Wang (Int. J. Found. Comput. Sci., 2005)

Regular Expressions: New Results and Open Problems. - Keith Ellul; Bryan Krawetz; Jeffrey O. Shallit; Ming-wei Wang (J. Autom. Lang. Comb., 2005)