@article{eprints3884,
           title = {Preferences and normal goods: An easy-to-check necessary and sufficient condition},
          author = {Ennio Bilancini and Leonardo Boncinelli},
          number = {1},
            year = {2010},
         journal = {Economics Letters},
       publisher = {Elsevier},
          volume = {108},
           pages = {13--15},
             url = {http://eprints.imtlucca.it/3884/},
        keywords = {Normal goods; Bordered Hessian},
        abstract = {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.}
}