1. Online Etymology Dictionary.
https://www.etymonline.com/word/transaction
2. Wiktionary.
https://en.wiktionary.org/wiki/transact#English
3. BusinessDictionary.
http://www.businessdictionary.com/definition/transaction.html
4. Gray, J.: The transaction concept: virtues and limitations. In: Proceedings of Seventh International Conference on Very Large Databases, September 1981. Published by Tandem Computers Incorporated (1981)
5. https://mfiles.pl/pl/index.php/Transakcja