Peter has called my attention to the existence of some historical notes in the preface to the TAC reprint (TR-3) of Abelian categories. In particular, he had already essentially discovered the general adjoint functor, at least for reflective subcategories) in his undergrad honors thesis, even though adjoints had not yet been defined. The preface in the TAC reprint includes things not in any other published version of the book. Michael You're receiving this message because you're a member of the Categories mailing list group from Macquarie University. To take part in this conversation, reply all to this message. View group files<https://outlook.office365.com/owa/categories@mq.edu.au/groupsubscription.ashx?source=EscalatedMessage&action=files&GuestId=6bf90c14-94d1-45b7-a0b5-9dd447734d27> | Leave group<https://outlook.office365.com/owa/categories@mq.edu.au/groupsubscription.ashx?source=EscalatedMessage&action=leave&GuestId=6bf90c14-94d1-45b7-a0b5-9dd447734d27> | Learn more about Microsoft 365 Groups<https://aka.ms/o365g>