  We describe the extension to multiple datasets of a coherent method for the
search of continuous gravitational wave signals, based on the computation of
5-vectors. In particular, we show how to coherently combine different datasets
belonging to the same detector or to different detectors. In the latter case
the coherent combination is the way to have the maximum increase in
signal-to-noise ratio. If the datasets belong to the same detector the
advantage comes mainly from the properties of a quantity called {\it coherence}
which is helpful (in both cases, in fact) in rejecting false candidates. The
method has been tested searching for simulated signals injected in Gaussian
noise and the results of the simulations are discussed.
