  We show how to construct covariant amplitudes for processes involving higher
spins in this paper. First we give the explicit expressions of Rarita-Schwinger
wave functions and propagators for bosons with spins, then kinematic
singularity free 3-leg effective vertexes are derived and given in a list.
Equivalence relations are worked out to get these independent vertexes.
Constraints of space reflection symmetry and boson symmetry are considered and
shown in a explicit way. Some helicity amplitudes for two-body decays in center
of frame are calculated. Finally the covariant helicity amplitudes for the
process $a_1\to \pi^+\pi^+\pi^-$ are constructed to illustrate how to include
background (1PI) amplitudes. Both background amplitudes and resonance
amplitudes are needed to give reliable descriptions to high energy reactions.
