, F. Combes
Onsala Space Observatory, S--43992 Onsala, Sweden 
DEMIRM, Observatoire de Paris, 61 Av. de l'Observatoire,
F--75014 Paris, France 
(1--2) and HCN(1--2)
have been detected at a redshift of
towards the background
BLLac object B0218+357. The CO and HCN lines are strongly saturated, while
the HCO
line is mildly saturated
(Fig 5). Lower limits to the column densities
are 
cm
for CO,
cm
for HCO
and
cm
for HCN.
The filling factor for the background source is larger than 0.7--0.8.
The absorption line profile is asymmetric with a width of 
kms
.
B0218+357 is a gravitational lens candidate with two compact continuum sources
separated by 335mas (1.8kpc). The small linewidth of the molecular
absorption puts constraints on the inclination and position angle of the
lensing galaxy.
We also report a search for QSOs molecular absorption lines in 12 other
redshifted systems; none were detected.
Figure: Low resolution spectra of a) HCN (J=1-2), 
kms
,
and b) HCO
, 
kms
, towards B0218+357. The velocity
scale in heliocentric and centered at 