What is the ruling on creating summarized notes of professors' books and selling them to students, with the addition of a personal style and extra information, and at a symbolic price?

It is permissible to summarize books, add information to them, and sell them to students, and this is not considered an infringement of the author's rights. The author's permission is not required for quoting; rather, attributing the statements to their originators is what is required. If the author publishes his book, this implies his permission for its contents to be utilized. Benefiting from information and quoting from it is not considered an infringement of his right. What is forbidden is printing the book and selling it without his permission.