http://help-legacy.sap.com/abapdocu_750/en/index.htm
https://wiki.scn.sap.com/wiki/display/ABAP/ABAP+Development
https://wiki.scn.sap.com/wiki/display/ABAP/ABAP+Objects
http://zevolving.com/category/abapobjects/oo-design-patterns/
https://wiki.wdf.sap.corp/wiki/display/EHSArch/Steps+to+create+a+Fiori+App+with+CDS+views
http://www.sapyard.com/logical-lock-vs-physical-lock-in-sap/
http://help.sap.com/abapdocu_750/en/index.htm?file=abenabap_json_sxml.htm