@article{10_1017_S204061850003375X,
     author = {Putnam, C. R.},
     title = {On {Square} {Roots} and {Logarithms} of {Self-Adjoint} {Operators}},
     journal = {Glasgow mathematical journal},
     pages = {1--2},
     year = {1958},
     volume = {4},
     number = {1},
     doi = {10.1017/S204061850003375X},
     url = {http://geodesic.mathdoc.fr/articles/10.1017/S204061850003375X/}
}