2009 · Stephen R. Durham, Ronald Dahl, et al. · University of Groningen research database (University of Groningen / Centre for Information Technology) · 3
2009 · Ronald Dahl, Stephen R. Durham, et al. · University of Groningen research database (University of Groningen / Centre for Information Technology)
2007 · W. Emminger, Rasmus Holmboe Dahl, et al. · University of Groningen research database (University of Groningen / Centre for Information Technology)