Is there a definitive reference for Turing machines with multiple oracle tapes?
Here is a more recent paper giving a difference between single vs. multiple oracles motivated by cryptography:

Donald Beaver and Joan Feigenbaum.  Hiding instances in multioracle queries.  STACS 1990.  Springer Lecture Notes in Computer Science, 1990, Volume 415/1990, 37-48, DOI: 10.1007/3-540-52282-4_30