@article{700139,
     title = {Bifurcations near a double eigenvalue of the rectangular plate problem with a domain parametr},
     booktitle = {Equadiff 6},
     series = {GDML\_Books},
     publisher = {J. E. Purkyn\v e University, Department of Mathematics},
     address = {Brno},
     year = {1986},
     pages = {[415]-420},
     mrnumber = {MR0877157},
     zbl = {0604.73050},
     url = {http://dml.mathdoc.fr/item/700139}
}

Sadovský, Zoltán. Bifurcations near a double eigenvalue of the rectangular plate problem with a domain parametr, dans Equadiff 6, GDML_Books,  (1986), pp. [415]-420. http://gdmltest.u-ga.fr/item/700139/