Kortmann, Bernd. 1997. Adverbial subordination: A typology and history of adverbial subordinators based on European languages. Berlin: Mouton de Gruyter.
https://www.degruyter.com/document/doi/10.1515/9783110812428/html
@book{kortmann_adverbial_1997,
address = {Berlin},
author = {Kortmann, Bernd},
publisher = {Mouton de Gruyter},
title = {Adverbial subordination: A typology and history of adverbial subordinators based on European languages},
url = {https://www.degruyter.com/document/doi/10.1515/9783110812428/html},
year = {1997},
isbn = {978-3-11-015114-5},
shorttitle = {Adverbial Subordination}
}