Ford 1999 Wagon-Econoline Owner's Manual page 90

Seating and safety restraints
Ford recommends the use of a child safety seat having a top tether
strap. Install the child safety seat in a seating position which is capable
of providing a tether anchorage. For more information on top tether
straps, refer to Attaching safety seats with tether straps.
Carefully follow all of the manufacturer's instructions included
with the safety seat you put in your vehicle. If you do not install
and use the safety seat properly, the child may be injured in a sudden
stop or collision.
Installing child safety seats in combination lap and shoulder belt
seating positions
1. Position the child safety seat in a
seat with a combination lap and
shoulder belt.
An air bag can kill or injure a child in a child seat. If you must
use a forward-facing child seat in the front seat, move seat all
the way back.
Children 12 and under should be properly restrained in the rear
seat whenever possible.
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