CITROËN 2014 C4 Picasso Handbook page 252

Safety
IUF: seat suitable for the installation of an
isoFiX Universal seat, "Forward facing"
secured using the upper strap to the top tether
on ISOFIX seats.
IL-SU: seat suitable for the installation of an
Isofix Semi-Universal seat either:
- rearward facing fitted with an upper strap
or a support leg,
- forward facing fitted with a support leg,
- a sleeper cot fitted with an upper strap or a
support leg.
250
For advice on securing the upper strap, refer to
the "Isofix Mountings" section.
X: seat not suitable for the installation of a
child seat or sleeper cot for the weight group
indicated.
Remove and stow the head restraint
before installing a child seat on a
passenger seat. Refit the head restraint
once the child seat has been removed.