@article{10_4153_CJM_1970_122_7,
     author = {Derzko, N. A.},
     title = {Gentle {Perturbations} of with {Application} to},
     journal = {Canadian journal of mathematics},
     pages = {1055--1070},
     year = {1970},
     volume = {22},
     number = {5},
     doi = {10.4153/CJM-1970-122-7},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CJM-1970-122-7/}
}