intergalactic gas, quasars, and other objects will be presented, and their chemical and structural nature discussed.
interplanetary scintillation; finding quasars as stars with strange spectra.
Several strong candidates for Type 2, or obscured quasars have been discovered.
finding the powerful quasars responsible for the X-ray background radiation.
The total number of ROSAT detected radio quasars from the above three sources is 654 objects.