  The Resonating Valence Bond (RVB) theory for two-dimensional quantum
antiferromagnets is shown to be the correct paradigm for large enough ``quantum
frustration''. This scenario, proposed long time ago but never confirmed by
microscopic calculations, is very strongly supported by a new type of
variational wave function, which is extremely close to the exact ground state
of the $J_1{-}J_2$ Heisenberg model for $0.4 \lesssim J_2/J_1\lesssim 0.5$.
This wave function is proposed to represent the generic spin-half RVB ground
state in spin liquids.
