  A new approach to the problem of gravitational waves detection based on
simultaneous timing of several pulsars and subsequent expansion of the post-fit
timing data into components of different spectral kind (with different spectral
indices) is proposed. Presence of a signal caused by stochastic gravitational
waves in spectral components is tested with the two-point angular correlation
function as proposed in the pulsar timing array. This new approach was applied
to timing data of a few millisecond pulsars and allowed to detect a signature
similar to one predicted for gravitational wave background at relatively high
confidence level: correlation coefficient between experimental and theoretical
two-point correlations $\rho=0.82\pm 0.07$.
