@article{10_1017_S0017089510000728,
     author = {HEJUN, SUN and XUERONG, QI},
     title = {EIGENVALUE {ESTIMATES} {FOR} {QUADRATIC} {POLYNOMIAL} {OPERATOR} {OF} {THE} {LAPLACIAN}},
     journal = {Glasgow mathematical journal},
     pages = {321--332},
     year = {2011},
     volume = {53},
     number = {2},
     doi = {10.1017/S0017089510000728},
     url = {http://geodesic.mathdoc.fr/articles/10.1017/S0017089510000728/}
}