@article{700161,
     title = {The convergence of a new method for calculating lower bounds to eigenvalues},
     booktitle = {Equadiff 6},
     series = {GDML\_Books},
     publisher = {J. E. Purkyn\v e University, Department of Mathematics},
     address = {Brno},
     year = {1986},
     pages = {[303]-308},
     mrnumber = {MR0877140},
     zbl = {0609.65072},
     url = {http://dml.mathdoc.fr/item/700161}
}

Goerisch, Friedrich; Albrecht, Julius. The convergence of a new method for calculating lower bounds to eigenvalues, dans Equadiff 6, GDML_Books,  (1986), pp. [303]-308. http://gdmltest.u-ga.fr/item/700161/