Ghillebaert, Saartje, and Klaas Willems. “Distinguishing between Obligatory and Optional Grammatical Categories in ’thinking for Speaking’ : The Use of the ‘Aan Het Construction’ by Six-Year-Old Flemish Children.” Annual Meeting of the Illinois Language and Linguistics Society, 13th, Proceedings, edited by Sarah Clark, vol. 44, 2021, pp. 61–90.