The graphic images illustrating the text belong to a collection of 30 litographs, produces by the artists exclusively for C. Lotti & Associati during the years 1963-1992 for use as Christmas gifts for our friends. In order, they are: 1) Fluens (P. D’Orazio, 1972); 2) Systematic (A. Perilli, 1975); 3) Acqua tra le rocce (P. Fazzini, 1964); 4) Tunnel in blu (G. Turcato, 1968); 5) Natura (A. Corpora, 1976); 6) Expressway (B. Liberatore, 1992).