They're rather working on the assumption that readers know that anything with a "(1)" or an "(8)" after it is a reference to a user manual. This is a very comm

They're rather working on the assumption that readers know that anything with a "(1)" or an "(8)" after it is a reference to a user manual. This is a very common thing in BSD doco, and in Unix doco more generally. For experienced Unix users this is likely to be true. It's something that one just learns. For novice users, it is less likely.