  The difference of the rest masses m(pi^+-) - m(mu^+-) is nearly equal to 1/4
of the rest mass of the pi^(+-) mesons and is equal to the sum of the rest
masses of the 0.7 times 10^9 muon neutrinos (respectively anti-muon neutrinos)
which are in the cubic lattice of the pi^(+-) mesons according to the standing
wave model. In the decay of a pi^(+) or pi^(-) meson all muon neutrinos,
respectively anti-muon neutrinos, of the cubic lattice of the pi^(+-) mesons
are emitted. The sum of the oscillation energies of all neutrinos in the
pi^(+-) mesons is the same as the sum of the oscillation energies of the
remaining neutrinos in the mu^(+-) mesons. Consequently the mass of the mu^(+-)
mesons is equal to m(pi^+-) - 0.7 times 10^9 m(nu_mu) or 0.75 times m(pi^+-),
within 1% in agreement with the measured ratio m(mu^+-) / m(pi^+-) = 0.757028.
