Generalized isobar model formalism

We present an isobar model formalism for analyzing the reaction $a + b\to 1 + 2 + 3$. Arbitrary spins are allowed for all the particles. Polarized particles and weak decays of an outgoing particle are discussed. We also show how to extend the formalism to allow an isobar analysis of a three-body subsystem of an $n$-particle final state.