books.google.de - A broad introduction to quadratic forms, modular functions, interpretation by rings and ideals, class fields by radicals and more. 1985 ed....http://books.google.de/books/about/Introduction_to_the_Construction_of_Clas.html?hl=de&id=ASWeWRzAhqgC&utm_source=gb-gplus-shareIntroduction to the Construction of Class Fields