According to https://en.wikipedia.org/wiki/Telephone_numbers_in_Europe and https://www.rtr.at/en/tk/E129/Austrian_Numbering_Plan_2011-03-30.pdf RTR being Austrian Regulatory Authority
According to https://en.wikipedia.org/wiki/Telephone_numbers_in_Europe and https://www.rtr.at/en/tk/E129/Austrian_Numbering_Plan_2011-03-30.pdf RTR being Austrian Regulatory Authority