CITROËN DS4 Owner's Handbook Manual page 166

Locations for child seats secured using the seat belt
In accordance with European regulations, this table indicates the options for installing child seats secured using the seat belt and universally approved (a)
in relation to the weight of the child and the seat in the vehicle.
Seat
Front passenger seat (c)
- fixed
- height adjustable
Outer rear seats
Centre rear seat
(a) Universal child seat: child seat which can be installed in all vehicles using the seat belt.
(b) Group 0: from birth to 10 kg. Infant car seats and "car cots" cannot be installed on the front passenger seat.
(c) Consult the legislation in force in your country before installing your child on this seat.
U : seat suitable for the installation of a child seat secured using the seat belt and universally approved "rear facing" and/or "forward facing".
U(R1) : identical to U , with the vehicle's seat backrest inclined fully forwards.
U(R2) : identical to U , with the vehicle's seat adjusted to the highest position.
X : seating position not suitable for installing a child seat for the weight group indicated.
Less than 13 kg From 9 to 18 kg
(groups 0 (b) and 0+)
Up to ≈ 1 year From 1 to ≈ 3 years
U(R1)
U(R2)
U
X
Weight of the child/ indicative age
From 15 to 25 kg
(group 1) (group 2)
From 3 to ≈ 6 years
U(R1) U(R1)
U(R2) U(R2)
U U
X X
From 22 to 36 kg
(group 3)
From 6 to ≈ 10 years
U(R1)
U(R2)
U
X