Editorial – Special Issue on Contracts on Digital Goods and Services Metzger Axel Schweitzer Heike 340 periodical academic journal JIPITEC 8 1 2017 1 1 2190-3387 urn:nbn:de:0009-29-45270 http://nbn-resolving.de/urn:nbn:de:0009-29-45270 metzger2017