@article{MS2_1972__31_166270,
     author = {Viggo Brun and Finn F. Knudsen},
     title = {On the {Possibility} of {Finding} {Certain} {Criteria} for the {Irrationality} of a {Number} {Defined} as a {Limit} of a {Sequence} of {Rational} {Numbers.}},
     journal = {Mathematica Scandinavica},
     pages = {231--236},
     publisher = {mathdoc},
     volume = {31},
     year = {1972},
     zbl = {0252.10030},
     url = {http://geodesic.mathdoc.fr/item/MS2_1972__31_166270/}
}