tar -xvf gsl-2.6.tar.gz
cd gsl-2.6
./configure --prefix=/path/to/EXTRA/GSL
make make install
unset LDFLAGS CFLAGS CXXFLAGS FCFLAGS LIBS
export LIBRARY_PATH=/path/to/EXTRA/GSL/lib:$LIBRARY_PATH export LD_LIBRARY_PATH=/path/to/EXTRA/GSL/lib:$LD_LIBRARY_PATH