This sub-directory first appeared in Version 2.12, when the RESPA subroutines were separated from the source directory to make construction of the RESPA program simpler. The respa sub-directory consists of the subroutines unique to the RESPA application. The RESPA makefile (Makefile_respa in the build sub-directory has been designed to gather the additional subroutines required from the source sub-directory at compile time. It is not necessary for the user to copy them over.