anchor.diff:  C       =======================================================
   C       Purpose: Integrate modified Bessel functions I0(t) and
   C                K0(t) with respect to t from 0 to x
  -C       Input :  x  --- Upper limit of the integral  ( x  0 )
  +C       Input :  x  --- Upper limit of the integral  ( x ≥ 0 )
   C       Output:  TI --- Integration of I0(t) from 0 to x
   C                TK --- Integration of K0(t) from 0 to x
   C       =======================================================
  
positive.code: C       Purpose: Compute Jacobian elliptic functions sn u, cn u
  C                and dn u
  C       Input  : u   --- Argument of Jacobian elliptic fuctions
  C                Hk  --- Modulus k ( 0  k  1 )
  C       Output : ESN --- sn u
  C                ECN --- cn u
  C                EDN --- dn u
  
negative.code: C
  C       =====================================================
  C       Purpose: Compute Legendre functions Qn(x) and Qn'(x)
  C       Input :  x  --- Argument of Qn(x) ( -1 ≤ x ≤ 1 )
  C                n  --- Degree of Qn(x) ( n = 0,1,2,… )
  C       Output:  QN(n) --- Qn(x)
  C                QD(n) --- Qn'(x)
  C                ( 1.0D+300 stands for infinity )
  