1. Über die Formänderung dünnwandiger Röhre insbesonders federnder angleischröhre;Von Karman;Zeit. Ver. Dent. Ing.,1911
2. Characteristics of short radius tube bends;Symonds;US Naval Research Laboratory Report 0-2761, Washington, D.C.,1946
3. In-plane bending properties of welding elbows;Pardue;Trans. ASME,1955
4. Experimental study of flexibility factors and stresses of welding elbows with end effects;Imamasa,1973
5. The effects of flanges on smooth pipe bends in piping systems;Findlay,1973