  Resonating valence bond states in a doped Mott insulator was proposed to
explain superconductivity in cuprates in January 1987 by Anderson. A
challenging task then was proving existence of this unconventional mechanism
and a wealth of possibilities, with a rigor acceptable in standard condensed
matter physics, in a microscopic theory and develop suitable many body
techniques. Shortly, a paper by Anderson, Zou and us (BZA) undertook this task
and initiated a program. Three key papers that followed, shortly, essentially
completed the program, as far as superconductivity is concerned: i) a gauge
theory approach by Anderson and us, that went beyond mean field theory ii)
Kotliar's d-wave solution in BZA theory iii) improvement of a renormalized
Hamiltonian in BZA theory, using a Gutzwiller approximation by Zhang, Gros,
Rice and Shiba. In this article I shall focus on the merits of BZA and gauge
theory papers. They turned out to be a foundation for subsequent developments
dealing with more aspects that were unconventional - d-wave order parameter
with nodal Bogoliubov quasi particles, Affleck-Marston's $\pi$-flux condensed
spin liquid phase, unconventional spin-1 collective mode at $(\pi,\pi)$, and
other fascinating developments. Kivelson, Rokhsar and Sethna's idea of holons
and their bose condensation found expression in the slave boson formalism and
lead to results similar to BZA program. Further, t-J model is a good minimal
model around optimal doping, where RVB superconductivity is also at its best.
