http://orgmode.org/manual/System_002dwide-header-arguments.html#System_002dwide-header-arguments Org Mode Info System-wide header arguments ............................
System-wide values of header arguments can be specified by customizing the `org-babel-default-header-args' variable: ;;;;; Seems not the case as in ob-core.el (defvar org-babel-default-header-args ;;;;;
