Did you know that hydropneumatic suspension was tested on non-Citroën cars in the 80s?
Volvo was testing it in a modified 740 model where under the hood, hydraulic struts were fitted in place of the stock MacPherson struts.
101 Trivial Car Facts
If you can spare about 20 minutes from your obsession with Citroën, check out this video that provides 101 trivial facts about automobiles