FUNCTION LEGENDRE,X,L,M
;
	IF N_PARAMS(0) LT 2 THEN BEGIN
		PRINT,'*** LEGENDRE must be called with 2-3 parameters:'
		PRINT,'                 X, L  [, M ]'
		RETURN,X
	END ELSE IF N_PARAMS(0) EQ 2 THEN M = 0
;
	IF M LT 0 THEN BEGIN
		PRINT,'*** M must not be less than 0, routine LEGENDRE.'
		RETURN,X
	END ELSE IF M GT L THEN BEGIN
		PRINT,'*** M must not be greater than L, routine LEGENDRE.'
		RETURN,X
	END ELSE BEGIN
		S = SIZE(X)
		IF S(0) EQ 0 THEN TEST = ABS(X) ELSE TEST = MAX(ABS(X))
		IF TEST GT 1 THEN BEGIN
			PRINT,'*** X must be in the range -1 to 1, routine LEGENDRE.'
			RETURN,X
		ENDIF
	ENDELSE
;
	PMM = 0.*X + 1.
	IF M GT 0 THEN BEGIN
		SOMX2 = SQRT( (1. - X) * (1. + X) )
		FACT = 1.
		FOR I = 1,M DO BEGIN
			PMM = -PMM*FACT*SOMX2
			FACT = FACT + 2.
		ENDFOR
	ENDIF
;
	IF L EQ M THEN PLGNDR = PMM ELSE BEGIN
		PMMP1 = X * (2*M + 1) * PMM
		IF L EQ M+1 THEN PLGNDR = PMMP1 ELSE BEGIN
			FOR LL = M+2,L DO BEGIN
				PLL = (X*(2*LL-1)*PMMP1 - (LL+M-1)*PMM) / (LL-M)
				PMM = PMMP1
				PMMP1 = PLL
			ENDFOR
			PLGNDR = PLL
		ENDELSE
	ENDELSE
;
	RETURN,PLGNDR
	END