The first detection of HI in a quasar spectrum was made by Brown &
Roberts (1973), who detected a narrow absorption line against 3C286 at a
red-shift of z=0.69.
HI absorption has also been detected against the QSO PKS 1157+014
(Wolfe, Briggs & Jauncey 1981) and the BL Lac object AO 0235+164 (Wolfe,
Davis & Briggs 1982). For a summary see e.g., Giovanelli & Haynes (1988).
Another very interesting study is that of HI absorption lines against
strong radio continuum sources, many of them quasars, in the vicinity of
spiral galaxies; see e.g., Corbelli & Schneider (1990) and Dickey, Brinks
& Puche (1992).
