  It has been shown that velocity of propagation of wave front cannot coincide
with observable velocity of quantum particles. It is additional argument leads
to conclusion that phase wave of de Broglie cannot be associated with single
"elementary" particle like electron. Therefore quantum interference under
linear superposition cannot describe energy distribution in extended quantum
particles. Essentially new approach is required in order to establish
non-linear relativistic wave equations with soliton-like solutions.
