Ask HN: Which are the best resources to learn software architecture?

I'm a software engineer with ~4 years of experience in the IT industry. Since I've always liked designing systems (of any kind), I'm thinking I'd love moving to a software architect role. Currently I'm working closely with some software architects and I guess this can count as practice. But what about theory? Which are the resources (courses, books, etc.) that helped you become a great software architect?