@article{10_4153_S0008414X22000293,
     author = {Bush, Michael and Frymark, Dale and Liaw, Constanze},
     title = {Singular boundary conditions for {Sturm{\textendash}Liouville} operators via perturbation theory},
     journal = {Canadian journal of mathematics},
     pages = {1110--1146},
     year = {2023},
     volume = {75},
     number = {4},
     doi = {10.4153/S0008414X22000293},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/S0008414X22000293/}
}