Silvia Biasotti Leila De Floriani Bianca Falcidieno Patrizio Frosini Daniela Giorgi Claudia Landi Laura Papaleo Michela Spagnuolo Describing shapes by geometrical-topological properties of real functions. 2008 40 ACM Comput. Surv. 4 http://doi.acm.org/10.1145/1391729.1391731 db/journals/csur/csur40.html#BiasottiFFFGLPS08