  We investigate the bounds on light pseudoscalars that arise from a variety of
collider searches. Special attention is thereby devoted to the mass regions
$[3, 5] \, {\rm GeV}$ and $[9,11] \, {\rm GeV}$, in which a meaningful
theoretical description has to include estimates of non-perturbative effects
such as the mixing of the pseudoscalar with QCD bound states. A compendium of
formulas that allows to deal with the relevant corrections is provided. It
should prove useful for the interpretation of future LHC searches for light
CP-odd spin-0 states.
