[1] J. A. Bather: On the sequential construction of an optimal age replacement policy. Proc. 41st Session ISI, New Delhi 1977. MR 0617579

[2] P. Mandl: On the sequential improvement of replacement policies. Proc. Second Prague Symp. on Asymptotic Statistics JČSMF - North Holland, Prague 1979. MR 0571195 | Zbl 0431.60086

[3] V. Menyhértová: A contribution to the theory of preventive replacement of machine parts. (In Slovak.) Thesis, Charles University, Prague 1979.