Williams, E. H., & Bunkley-Williams, L. (2006). Three anomalies: A scythebill in the Greater Antillean Grackle (blackbird), a crown pattern in the Rock Beauty (angelfish), and a double spot in the Butter Hamlet (grouper), and their possible genetic significance. Universidad de Costa Rica.

Williams, Ernest H., and Lucy Bunkley-Williams. Three Anomalies: A Scythebill in the Greater Antillean Grackle (blackbird), a Crown Pattern in the Rock Beauty (angelfish), and a Double Spot in the Butter Hamlet (grouper), and Their Possible Genetic Significance. Universidad de Costa Rica, 2006.

Williams, Ernest H., and Lucy Bunkley-Williams. Three Anomalies: A Scythebill in the Greater Antillean Grackle (blackbird), a Crown Pattern in the Rock Beauty (angelfish), and a Double Spot in the Butter Hamlet (grouper), and Their Possible Genetic Significance. Universidad de Costa Rica, 2006.