1. 1957 Prager, W., “Ideal locking materials”, Trans.Soc.Rheol., 1, 169.
2. 1975 Maier, G., “Mathematical programming methods in analysis of elastic-plastic structures” (in Polish), Arch. In¿. L1d., 31, 387.
3. 1978 König, JA. and KLEIBER M., “On a new method of shakedown analysis”, Bull. Polon. Acad., Sci. Ser. Sci. Tech., 26, 165.
4. 1983 Gawęcki A., “Nonlinear effects of joint clearances on behaviour of bar structures”, 24-th Polish Solid Mech. Conf., Jachranka (Poland)
5. 1985 Borkowski, A., “Analysis of Skeletal Structural Systems in the Elastic and Plastic Ranges” (in Polish), 1-st ed., PWN, Warszawa-Poznañ, pp. 200.