CITROËN C4 Handbook page 158

Safety
Child seat at the rear
Rearward facing
When a rearward facing child seat is installed
on a rear passenger seat, move the vehicle's
front seat forward and straighten the backrest
so that the rearward facing child seat does not
touch the vehicle's front seat.
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Forward facing
When a forward facing child seat is installed
on a rear passenger seat, move the vehicle's
front seat forward and straighten the backrest
so that the legs of the child in the forward
facing child seat do not touch the vehicle's front
seat.
Ensure that the seat belt is correctly
tensioned.
For child seats with a support leg,
ensure that this is in firm contact with
the floor. If necessary, adjust the front
seat of the vehicle.
Centre rear seat
A child seat with a support leg must never be
installed on the centre rear passenger seat.
The incorrect installation of a child seat
in a vehicle compromises the protection
of the child in the event of an accident.