As I promised (to myself mostly) I uploaded the Valve studio profile we (Shenja van der Graaf and I) did for GMR magazine. It’s downloadable here in .pdf. The two paged story is on how Valve works and a bit on the making (and testing of Portal). Exact reference is: ‘Ontwikkelaarsprofiel: Valve Software‘. In: GMR. 2.5, 2007, page 40-41.