Netherlands - 2013 Party Finance Law

Title Article 2
Chapter ? 1. General provisions
Article

2

1. A political party may designate one political-scientific institute as a subsidiary institution. A political-scientific institute may not be designated by more than one political party and the institute shall accept the designation in writing. The party shall inform Our Minister, in writing, as to the designation and acceptance thereof by the institute.
2. In order that a political-scientific institute may be designated as a subsidiary institution, the institute is required to be a legal person which exclusively or principally carries out political-scientific activities for the benefit of the political party.

Categories - Extra-parliamentary party (Organizational structure)
Source https://zoek.officielebekendmakingen.nl/stb-2013-93.html