c----------------------------------------------------------------------
	function DERFXP(x)
c  yields the derivative d/dx erfx(x)
c
c
c  author: Heiko Appel,  5.18.99
c      in: x - argument for the derivative
c     out: return value of function: value of the derivative of the 
c          error function at x	
c   calls: --
	implicit real*8 (a-h,o-z)