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SUBROUTINE DLGAM

PURPOSE
   COMPUTES THE DOUBLE PRECISION NATURAL LOGARITHM OF THE
   GAMMA FUNCTION OF A GIVEN DOUBLE PRECISION ARGUMENT.

USAGE
   CALL DLGAM(XX,DLNG,IER)

DESCRIPTION OF PARAMETERS
   XX	- THE DOUBLE PRECISION ARGUMENT FOR THE LOG GAMMA
	  FUNCTION.
   DLNG - THE RESULTANT DOUBLE PRECISION LOG GAMMA FUNCTION
	  VALUE.
   IER	- RESULTANT ERROR CODE WHERE
	  IER= 0----NO ERROR.
	  IER=-1----XX IS WITHIN 10**(-9) OF BEING ZERO OR XX
		    IS NEGATIVE.  DLNG IS SET TO -1.OD75.
	  IER=+1----XX IS GREATER THAN 10**70. DLNG IS SET TO
		    +1.OD75.

REMARKS
   NONE

SUBROUTINES AND FUNCTION SUBPROGRAMS REQUIRED
   NONE

METHOD
   THE EULER-MCLAURIN EXPANSION TO THE SEVENTH DERIVATIVE TERM
   IS USED, AS GIVEN BY M. ABRAMOWITZ AND I.A. STEGUN,
   'HANDBOOK OF MATHEMATICAL FUNCTIONS', U. S. DEPARTMENT OF
   COMMERCE, NATIONAL BUREAU OF STANDARDS APPLIED MATHEMATICS
   SERIES, 1966, EQUATION 6.1.41.