Marek Weretka has presented his theoretical findings on quasi-linear approximations. The speech as well as the accompanying paper focuses on the complete markets setups within, be it, single agent problem (small open economy) or general equilibrium with endogenous prices (large closed economy). Marek also casted some light on current work in progress in our INFERENCE project, namely the importance and a simplifying potential of quasilinear approximations in incomplete markets setups as in Bewley-Huggett-Aiyagari type of models.