In one of his later books, Larry Niven thanks some people for proof-reading and says "Where were you when I wrote 'Ringworld'?"

In the next paragraph he tells owners of the first edition of "Ringworld" to hang onto it, as it's the only edition in which he has the world rotating the wrong way.

Presumably this is in the opening chapter where Louis Wu is chasing the terminator round the planet to stretch his birthday celebrations out.