@book{Ruskin, author = {Ruskin, J.}, title = {The Elements of Drawing. The Elements of Perspective, London (J.M.Dent and Sons) and New York (E.P. Dutton and Co.) 1932.}, language = {en} } @book{EdwardRuskinTurrini, author = {Edward, J. and Ruskin, N. and Turrini, P.}, title = {Separation-Individuation. Theory and Application. New York (Gardner) 1981.}, language = {en} }