You may want to begin with a

review
written by Distinguished Professor K. Likharev.

Brief history of RSFQ

• 1911 — Kammerling Onnes discovers superconductivity
• 1962 — B. Josephson predicts the quantum effects that have his
  name
• 1976 — K. Nakajima, Y. Onodera, and Y. Ogawa, article on “Logic
  design of Josephson network” (J. Appl. Phys. 47, 1620-1627)
• 1978 — K. Nakajima and Y. Onodera, article on “Logic design of
  Josephson network – II” (J. Appl. Phys. 49, 2958-2963)
• 1978 — A. Silver proposes the first RSFQ circuit — a T
  flip-flop
• 1983 — K. Nakajima, G. Oya, and Y. Sawada, article on “Fluxoid
  motion in phase mode Josephson switching system” (IEEE Trans. on Magn.
  19, 1201-1204)
• 1983 — HYPRES founded
• 1985 — the first article
  on RSFQ