  We present the results of the Neutrino-4 experiment on search for a sterile
neutrino. The experiment has been carried out on the SM-3 reactor having a
compact active zone of $42\times42\times35\textrm{cm}^3$ and operating on the
highly enriched uranium-235 at 90 MW thermal power. We report the results of
the Neutrino-4 experiment of measurements of reactor antineutrino flux and
spectrum dependence on the distance in the range 6-12 meters from the center of
the reactor core. Using the measured spectrum and the distance dependence of
antineutrino flux, we performed the model independent analysis of restrictions
on the oscillation parameters $\Delta m^2_{14}$ and $\sin^2 2\theta_{14}$. The
method of coherent addition of results of measurements is proposed. It allows
us to directly observe the effect of oscillations. We observed the oscillation
effect at CL $3.5\sigma$ in the vicinity of $\Delta m^2_{14} \approx
7.26\textrm{eV}^2$ and $\sin^2 2\theta_{14} \approx 0.38$. Combining the result
of the Neutrino-4 experiment and the result of the gallium anomaly effect we
obtained value $\sin^2 2\theta_{14} \approx 0.35 \pm 0.07 (5\sigma)$. The
analysis of systematics effects is presented. Comparison with results of other
experiments is presented. Future prospect of the experiment is discussed. It is
necessary to notice that obtained values $\sin^2 2\theta_{14} \approx 0.35 \pm
0.07 (5\sigma)$ and $\Delta m^2_{14} \approx (7.3 \pm 0.7)\textrm{eV}^2$ allow
make assessment on the mass of a neutrino: $m_{\beta} \approx 0.8\textrm{eV}$.
