Use Item Links Effectively
DEVONthink allows you to get a URL for any document or group stored in your databases. Select the item, then choose Edit > Copy Item Link. Then paste this link into any other suitable application, e.g. the URL field of an appointment in Calendar, a website field in Contacts, or the notes field of an OmniFocus task.
Power user Luc Beaulieu uses item links in BusyCal and BusyContacts. Now when the appointment is due, you start working on the task, or talk to your client you can bring up the linked document or group with a single click.