- https://www.lucidchart.com/pages/bpmn/gateways
- http://www.ariscommunity.com/users/frank-neubueser/2010-03-29-when-use-message-events
- https://www.visual-paradigm.com/tutorials/from-business-process-to-use-cases.jsp
- http://www.omg.org/news/meetings/workshops/SOA-HC/presentations-2011/14_MT-2_Brookshier.pdf
- http://www.bpmn-tool.com/en/tutorial/