Neutrinos are some of the most dificult to observe elementary particles.
They interact only weakly. Most of them escape without detection, only a tiny fraction of them can be seen.
There are three kinds of neutrinos: electron neutrino, muon neutrino and tau neutrino.
Neutrinos can oscillate i.e. they can change their identity in flight and transform from one kind of neutrino into another kind of neutrino.
Sources of observed neutrinos include: nuclear reactors, accelerator beams, radioactive sources, secondary particles created by interaction of cosmic rays in the atmosphere, Sun, supernovae.
Other possible soruces are: dark matter, gamma ray bursts, active galactic nuclei, relic neutrinos, Earth interior.
Comprehensive lists of references on the theory of neutrino oscillations, four-neutrino mixing, sterile neutrinos and others. www.to.infn.it/~giunti/NU
SuperNova Early Warning System; network utilizing existing detectors in coincidence to detect neutrino burst from supernova in order to provide alert to astronomers. hep.bu.edu/~snnet
For the detection of the neutrino by Professor Frederick Reines; description of the discovery and background material. nobelprize.org/physics/laureates/1995