Neutrino masses: theory and experiment

Assuming the premise that neutrinos do have mass the following questions are discussed in this Comment; How can neutrinos be given mass in the Weinberg-Salam model, are there bounds on the number of neutrino species, what are the cosmological implications of massive neutrinos, could they supply the missing mass to close the universe, what are neutrino oscillations and how might they be observed, can neutrino oscillations provide a solution to the solar neutrino problem, and what other new phenomena might a neutrino mass imply. (U.K.)