Cooling of neutron stars is calculated when the neutrino luminosity of
their cores is defined by the direct URCA process with neutrons and p
rotons and is partially suppressed by the simultaneous action of the s
uperfluidity of these particles. A comparison of theoretical cooling c
urves with the observed thermal emission of cool isolated neutron star
s poses restrictions on the critical temperatures T(cn) and T(cp) of t
he neutron and proton superfluidity, respectively, which arise in cent
ral parts of stars. Possible values of T(cn) and T(cp) for pulsar PSR
0656 + 14 are discussed.