Proof of the Picard-Lindelöf theorem: pdf file
Start of a self-contained introduction to algebraic geometry (including proofs of relevant theorems from commutative algebra): pdf file
Basics of the Jacobson radical in non-commutative algebra: pdf file
I volunteer for the Dutch mathematics magazine Pythagoras, where I mostly work on the Pythagoras Olympiade competition section.
I used to organise the dynamical systems seminars (DynamIC Seminars) at Imperial College London.