Short-baseline active-sterile neutrino oscillations?

We suggest the possibility that the anomalies in the LSND experiment and the Gallium radioactive source experiments may be due to neutrino oscillations generated by a large squared-mass difference of about 20-30 eV(2). We consider the simplest 3+1 four-neutrino scheme that can accommodate also the observed solar and atmospheric neutrino oscillations. We show that, in this framework, the disappearance nu((-))(e) and nu((-))(mu) in short-baseline neutrino oscillation experiments is mainly due to active-sterile transitions. The implications of the first MiniBooNE, appeared after the completion of this paper, are discussed in an addendum.