@article{10_4064_aa_13_4_395_404,
     author = {A. Rotkiewicz and H. Halberstam},
     title = {A gap theorem for pseudoprimes in arithmetic progressions},
     journal = {Acta Arithmetica},
     pages = {395--404},
     publisher = {mathdoc},
     volume = {13},
     number = {4},
     year = {1967},
     doi = {10.4064/aa-13-4-395-404},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/aa-13-4-395-404/}
}