It's my understanding that there were groups like the German Society for Racial Hygiene that promoted eugenics measures. I would assume that groups like this would use social Darwinism as a support for their theories. Can anyone recommend books on social Darwinism that a German eugenicist of the 1930s might have read, or any memorable quotes from social Darwinists that was used to support eugenics measures?

(I am a writer. I don't believe in any of these ideologies; I just want to be better informed)