Introduction to workflow
http://en.wikipedia.org/wiki/Workflow
http://www.e-workflow.org/bookstore/introduction_to_workflow02.pdf
http://blogs.msdn.com/davegreen/archive/2005/09/17/470704.aspx
http://www.aboutworkflow.com/WorkflowTutorial/index.htm
http://www.sqldts.com/287.aspx
http://www.e-workflow.org/standards/index.htm
Workflow Control-Flow Patterns
http://www.workflowpatterns.com/documentation/documents/BPM-06-22.pdf
http://www.workflowpatterns.com/patterns/control/index.php
http://www.workflowpatterns.com/documentation/index.php
http://en.wikipedia.org/wiki/Workflow_patterns (Good)
BPEL
Is BPEL the same as BPM, workflow or integration?
http://searchwebservices.techtarget.com/ateQuestionNResponse/0,289625,sid26_cid565868_tax292928,00.html
Service-Oriented Architecture-Concepts, Technology, and Design (book)
web Services Platform Arthitecture - SOAP, WSDL, WS-Policy, WS-Addressing, WS-BPEL, (book)
Implementation
Deploy distributed business processes with windows workflow and web service
http://msdn.microsoft.com/msdnmag/issues/06/10/webserviceworkflows/
http://blogs.msdn.com/publicsector/archive/2005/10/27/485691.aspx
Orchestrating Web Service
http://www.ftponline.com/xmlmag/2002_06/magazine/focus/sjohnston/default.aspx
Orchestration and Choreography
Service-Oriented Architecture - Concepts, Technology, and Design
Business processes and workflow in the Web services world
http://www.ibm.com/developerworks/webservices/library/ws-work.html