%P 13-15 %A Ennio Bilancini %A Leonardo Boncinelli %J Economics Letters %X We provide a necessary and sufficient condition for goods to be normal when utility functions are differentiable and strongly quasi-concave. Our condition is equivalent to the condition proposed by Alarie et al. (1990), but it is easier to check: it only requires to compute the minors associated with the border column (or row) of the bordered Hessian matrix of the utility function. %T Preferences and normal goods: An easy-to-check necessary and sufficient condition %V 108 %R doi:10.1016/j.econlet.2010.03.005 %N 1 %I Elsevier %L eprints3884 %D 2010 %K Normal goods; Bordered Hessian