A non local quantitative characterization of ellipses leading to a solvable differential relation. Amar, M.; Berrone, L.R.; Gianni, R. — 2008 JIPAM. Journal of Inequalities in Pure & Applied Mathematics [electronic only]
A notion of total variation depending on a metric with discontinuous coefficients M. Amar; G. Bellettini — 1994 Annales de l'I.H.P. Analyse non linéaire