@article{GDZPPN002045311,
title = {Some undecidable theories with monadic predicates and without equality.},
journal = {Archiv f\"ur mathematische Logik und Grundlagenforschung},
volume = {21},
year = {1981},
pages = {137-148},
zbl = {0475.03022},
url = {http://dml.mathdoc.fr/item/GDZPPN002045311}
}
Kleine Büning, Hans. Some undecidable theories with monadic predicates and without equality.. Archiv für mathematische Logik und Grundlagenforschung, Tome 21 (1981) pp. 137-148. http://gdmltest.u-ga.fr/item/GDZPPN002045311/