Appendix to “Amenable actions of real and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>p</mml:mi> </mml:math> -adic algebraic groups” by Alain Valette

As a complement to Alain Valette’s article, this appendix gives an extension from group actions to groupoids of Proposition 2.4. Namely, it is shown that, for a smooth, second countable, locally compact groupoid endowed with a Borel Haar system, measurewise amenability is equivalent to amenability of the isotropy subgroups.