@article{AMLG_1981__21_137976,
     author = {T.v.d. Twer},
     title = {On the strength of several versions of {Dirichlet's} (},
     journal = {Archiv f\"ur mathematische Logik und Grundlagenforschung},
     pages = {69--76},
     publisher = {mathdoc},
     volume = {21},
     year = {1981},
     zbl = {0467.03060},
     url = {http://geodesic.mathdoc.fr/item/AMLG_1981__21_137976/}
}