Schanz Georg. Zur Frage der Steuerpflicht in Finanzarchiv: Zeitschrift für das gesamte Finanzwesen. Stuttgart: Mohr, 1892. Vol. IX. Р. 287.

Tom Magney. Some Aspects of Source of Income (In the Last Decade of the Twentieth Century). 5th National Tax Retreat of the Taxation Institute of Australia, Queensland, 7–9 August 1997). P. 46: «[B]ehind all initiatings, negotiations and other activities leading to the conclusion of a transaction there must be activities (including decision making) by individuals (i.e. human beings) and it is where these individuals are physically located when the relevant activities take place or decisions are made which is of prime importance in determining the source of income».