this one is for the purists, "The Book of The Hackle " by Frank Elder,I bought my first capes from Him in the 6o's a Cochy Bondhu and an Iron blue, he was breeding for colour before the American Genetic breeders, and before they got round to Crossing in Yokohama Birds with the extreme hackle lengths,He was from round the Haddington Area, The book is out of print , but worth a read if you can get it, Derek Roxborough