That paper says “Algorithm R (which is a reservoir algorithm due to Alan Waterman)” but it doesn’t have a citation. Vitter’s previous paper https://dl.acm.org/doi/10.1145/358105.893 cites Knuth TAOCP vol 2. Knuth doesn’t have a citation.
> All in all, Algorithm R was known to Knuth and Waterman by 1975, and to a wider audience by 1981, when the second edition of The Art of Computer Programming volume 2 was published.