@article{AFM_1962_306-315_a9,
     author = {Klaus Vala},
     title = {On the {Gram} determinant and linear transformations of {Hilbert} space},
     journal = {Annales Fennici Mathematici},
     publisher = {mathdoc},
     volume = {306-315},
     year = {1962},
     doi = {10.5186/aasfm.1962.306},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.5186/aasfm.1962.306/}
}