anchor.diff:  C
   C       =============================================
   C       Purpose: Compute cosine and sine integrals
  -C                Si(x) and Ci(x) ( x  0 )
  +C                Si(x) and Ci(x) ( x ≥ 0 )
   C       Input :  x  --- Argument of Ci(x) and Si(x)
   C       Output:  CI --- Ci(x)
   C                SI --- Si(x)
  
positive.code: C       Input :  p  --- Parameter  ( p > 0 )
  C                q  --- Parameter  ( q > 0 )
  C       Output:  BT --- B(p,q)
  C       Routine called: GAMMA2 for computing (x)
  C       ==========================================
  C
          IMPLICIT DOUBLE PRECISION (A-H,O-Z)
  
negative.code:         SUBROUTINE PBWA(A,X,W1F,W1D,W2F,W2D)
  C
  C       ======================================================
  C       Purpose: Compute parabolic cylinder functions W(a,±x)
  C                and their derivatives
  C       Input  : a --- Parameter  ( 0 ≤ |a| ≤ 5 )
  C                x --- Argument of W(a,±x)  ( 0 ≤ |x| ≤ 5 )
  C       Output : W1F --- W(a,x)
  C                W1D --- W'(a,x)
  C                W2F --- W(a,-x)
  