Other correlation functions:
CGGP_internal_CorrMatCauchySQT(),
CGGP_internal_CorrMatCauchySQ(),
CGGP_internal_CorrMatCauchy(),
CGGP_internal_CorrMatMatern32(),
CGGP_internal_CorrMatMatern52(),
CGGP_internal_CorrMatPowerExp(),
CGGP_internal_CorrMatWendland0(),
CGGP_internal_CorrMatWendland1(),
CGGP_internal_CorrMatWendland2()