anchor.diff:  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       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 )
  
positive.code: C                kind and their derivatives
  C       Input:   x --- Argument of Riccati-Bessel function
  C                n --- Order of yn(x)
  C       Output:  RY(n) --- xyn(x)
  C                DY(n) --- [xyn(x)]'
  C                NM --- Highest order computed
  C       ========================================================
  C
  
negative.code: C
  C       =======================================================
  C       Purpose: Integrate Bessel functions J0(t) and Y0(t)
  C                with respect to t from 0 to x ( x ≥ 0 )
  C       Input :  x  --- Upper limit of the integral
  C       Output:  TJ --- Integration of J0(t) from 0 to x
  C                TY --- Integration of Y0(t) from 0 to x
  