+Summary of directory reference syntaxes
+---------------------------------------
+
+ In source tree In build tree
+ Relative Absolute Relative Absolute
+
+ &file $(abs)/&file
+ This directory &^/file &~/file &/file $(abs)/&/file
+ & ^ f g h & ~ f g h & f g h
+
+ Top level $(ts)/file $(ats)/file file $(abs)/file
+ f g h
+