Derry, Margaret Elsinor: Bred for perfection: shorthorn cattle, collies, and arabian horses since 1800. Baltimore 2003. Internet: https://books.google.de/books?id=Hvx4a1wwPwUC&printsec=frontcover&dq=Bred+for+Perfection.+Shorthorn+Cattle,+Collies,+and+Arabian+Horses+since+1800.&hl=en&sa=X&ved=0ahUKEwje04rs7LLTAhWD1BoKHQX_AGcQ6AEIJDAA#v=onepage&q&f=false.