Buick 2004 LeSabre Owner's Manual page 46

In order to use the LATCH system in your vehicle, you
need a child restraint designed for that system.
1-40
To assist you in locating the lower anchors for this child
restraint system, each seating position with the
LATCH system has a label on the seatback at each
lower anchor position.
The labels are located
near the base of all three
rear seating positions.