subroutine nrmd
     m           (r1)
c
c     + + + PURPOSE + + +
c     Returns the standard normal deviate for a given probability value
c     (e.g. r1=.99 returns r1=2.328)
c
c     + + + ARGUMENT DECLARATIONS + + +
      real r1
c
c     + + + ARGUMENT DEFINITIONS + + +
c     r1          - initially, the probability; finally the std. norm. deviate.
c
c     + + + LOCAL VARIABLES + + +
      real sgn, hp,t
c     + + + LOCAL DEFINITIONS + + +

c     + + + END SPECIFICATIONS + + +
c
      if(r1 .ge. 0.5) then
        sgn = 1.0
        hp = 1.0 - r1
      else
        sgn = -1.0
        hp = r1
      endif 
      t = sqrt(alog(1./(hp*hp)))
      r1 = sgn*(t-(2.30753+.27061*t)/(1.+.99229*t+.04481*t*t))
      return
      end