[en] We investigate non-leptonic P-wave decays of hyperons induced by parity-conserving Cabibbo's weak Hamiltonian Hsup(p.c.), with the help of duality diagrams. The P-wave amplitudes thus obtained are found to be inconsistent with experiment. To overcome this difficulty, we propose the presence of a new parity-conserving weak Hamiltonian Hsup(p.c.) which induces lambda lambda→lambda n. (auth.)