I am trying to find a source for the old Pressure recuction values used in the days of the APN-85 for US airports (KPRC). These used the format of r=B0 - B1*Tav + B2 Tav^2. At the same time, I cannot seem to find out the magic formulas for reduction used today for Pst to Psl. I live near KPRC and fixed offset are out of the question. Any help would be appreciated.