SUBROUTINE source(it,jt,kt,isct,nm,Src,Srcx,Sigs,Flux,Pflux)
      IMPLICIT NONE
      INTEGER :: it, jt, kt, isct, nm
      DOUBLE PRECISION, DIMENSION(it,jt,kt) :: Srcx
      DOUBLE PRECISION, DIMENSION(it,jt,kt,isct + 1) :: Sigs
      DOUBLE PRECISION, DIMENSION(it,jt,kt,nm) :: Flux
      DOUBLE PRECISION, DIMENSION(it,jt,kt,nm) :: Src
      DOUBLE PRECISION, DIMENSION(it,jt,kt) :: Pflux
      INTEGER :: i, j, k
      IF (isct .EQ. 0) THEN
      DO k = 1, kt
      DO j = 1, jt
      DO i = 1, it