I have down-loaded and un-zipped Arduino 1.6.5-r5 to C:Program Files-A86. In the resulting /Arduino/libraries folder I have un-zipped an application into the .../libraries/SixDOF folder. Inside that folder is a "SixDOF_Example" file that, when run, fails because "No such file or directory can be found" for "FreeSixIMU.h". "FreeSixIMU.h" is an #include file in "SixDOF_Example". "FreeSixIMU.h" as well as two other #include files are in the .../SixDOF/FreeSixIMU directory.
Question: Where does Arduino look for #include files? Isn't one sub-directory close enough?