Earlier document exchange software from Hummingbird Ltd., Toronto, Ontario, (www.hummingbird.com) that converted a Windows or Macintosh document into a proprietary file format called DigitalPaper for viewing on other machines. The viewer allowed multiple documents to be displayed at the same time. Adobe's PDF file format became the industry standard for this function and caused Common Ground to become obsolete. In 2006, Hummingbird became a division of ECM software leader Open Text Corporation.