1. Influence and prevention of bird-droppings in precipitation chemistry experiments;Asman;Water Air Soil Poll,1982
2. The role of pigeon excrement in stone biodeterioration;Bassi;Int Biodetn Bull,1976
3. Feeding Trafalgar's pigeons illegal;BBC News,2003
4. Council in Pigeon Plea;BBC News,2004
5. Billmeyer and Saltzman's Principles of color technology;Berns,2000