SOCKET

Books
RPC- vs Document-Style Web Services
SOAP Headers

Russell Butek, May 2005, Which style of WSDL should I use?, retrieved online 23/02/06 at: http://www-128.ibm.com/developerworks/webservices/library/ws-whichwsdl/
Sameer Tyagi, Sept 2004, Patterns and Strategies for Building Document-Based Web Services: Part 1 in a Series, retrieved online 23/02/06 at: http://java.sun.com/developer/technicalArticles/xml/jaxrpcpatterns/index.html
Sameer Tyagi, Jan 2005, Interoperability With Patterns and Strategies for Document-Based Web Services: Part 2 in a Series, retrieved online 23/02/06 at: http://java.sun.com/developer/technicalArticles/xml/jaxrpcpatterns/index.html
Sameer Tyagi, Dec 2005, Realizing Strategies for Document-Based Web Services With JAX-WS 2.0: Part 3 in a Series, retrieved online 23/02/06 at: http://java.sun.com/developer/technicalArticles/xml/jaxrpcpatterns/index.html

SOAP Headers

Matt Powell, June 2002, Digging into SOAP Headers with the .NET Framework, retrieved online 08/03/06 at: http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnservice/html/service06182002.asp

Books

Kim Topley (2003), Java Web Services in a Nutshell, O'Reilly. Excellent book - especially for JAX-RPC, SAAJ, JAXM and JAXR.
Stephen Potts and Mike Kopack (2003), Teach Yourself Web Services in 24 Hours, SAMS. Reasonable text for a Web services newbie.
Inderjeet Singh, Sean Brydon, Greg Murray, Vijay Ramachandran, Thierry Violleau and Beth Stearns (2004), Designing Web Services with the J2EE 1.4 Platform, JAX-RPC, SOAP, and XML Technologies, SUN Microsystems, Addison Wesley. Good clear exposition; J2EE-oriented - lot more on design principles than most.