Intergovernmental agreements, called double taxation agreements (DTAs), exist to prevent double taxation of income from international activities. These agreements lay down which state (state of residence, or state in which income is generated) has a right of taxation, and which state has to fully or partially renounce its right to taxation. The purpose is effective one-off taxation.
Austria has concluded double taxation agreements with most states: 
List of Austrian Double Taxation Agreements (https://english.bmf.gv.at/taxation/Double-Taxation-Agreements.html)