“…This, together with other simplifying assumptions, leads to simple formulae for determining the required natural frequencies (Tarjan and Kollar, 2004). A useful tabulated summary of related work by the following authors is also included (Basu, 1983;Kopecsiri and Kollar, 1999a,b;Rosman, 1974;Rutenberg, 1975;Skattum, 1971;Smith and Crowe, 1986;Smith and Yoon, 1991;Zalka, 2001b).…”