1. Fattori di forma per alberi con variazione di diametro, soggetti a torsione;Giordano,1940
2. Torsional stress concentrations in shafts of circular cross-section and variable diameter;Jacobsen;Trans. Am. Soc. Mech. Engrs,1925
3. Zur Frage der Formziffer;Thum;Z. Ver. dt. Ing.,1935
4. Determination of the stress concentration factors of a stepped shift stressed in torsion by means of precision strain gauges;Weigand;Tech. Memo. Nat. Advis. Corn. Aer. Wash.,1944
5. Stress Concentration Design Factors;Peterson,1953