Buick 2008 Lucerne Owner's Manual page 50

The top tether anchors are located under the covers on
the rear seatback filler panel. Flip open the cover to
access the anchors. Be sure to use an anchor located
on the same side of the vehicle as the seating
position where the child restraint will be placed.
1-46
Do not secure a child restraint in a position without a
top tether anchor if a national or local law requires that
the top tether be attached, or if the instructions that
come with the child restraint say that the top tether must
be attached.
Accident statistics show that children are safer if they
are restrained in the rear rather than the front seat. See
Where to Put the Restraint on page 1-42 for additional
information.