Chromo- and Electrodynamics of Heavy Unstable Particle

In this talk I attempt to survey some selected physics issues on radiative interference phenomena in the production of heavy unstable particles. A special emphasis is placed on the reactions $e^+e^- \rightarrow W^+W^- \rightarrow 4$ jets and $e^+e^- \rightarrow t\bar{t} \rightarrow bW^+\bar{b}W^-$. A transparent recipe is given for quantifying the level of suppression of the interference effects in the inclusive production processes. The influence of the $W$ width on the Coulomb corrections to the threshold $W^+W^-$ production is briefly addressed.