Natural relations among physical observables in the neutrino mass matrix

We find all possible relations among physical observables arising from neutrino mass matrices that describe in a natural way the currently observed pattern (theta(23) and theta(12) large, Deltam(.)(2)/Deltam(Atm)(2) and theta(13) small) in terms of a minimum number of parameters. Natural here means due only to the relative smallness (vanishing) of some parameters in the relevant lagrangian, without special relations or accidental cancellations among them.