The impact of computers on productivity in the trade sector: explorations with Dutch microdata / Lourens Broersma and Robert H. McGuckinThe impact of computers on productivity in the trade sector : explorations with Dutch microdata / Lourens Broersma and Robert McGuckin" Changing gear" : productivity, ICT and services: Europe and the United States / Bart van Ark, Robert Inklaar and Robert McGuckinICT and productivity in Europe and the United States ; where do the differnce come from? / Bart van Ark, Robert Inklaar, Robert H. McGuckin