@article{10_4153_CMB_1992_046_0,
     author = {Fegan, H. D.},
     title = {Second {Order} {Operators} with {Non-Zero} {Eta} {Invariant}},
     journal = {Canadian mathematical bulletin},
     pages = {341--353},
     year = {1992},
     volume = {35},
     number = {3},
     doi = {10.4153/CMB-1992-046-0},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CMB-1992-046-0/}
}