comment	SP 139, see descr 23;
	real procedure PHI(x);value x;real x;
	begin	real z;

		z:=abs(x)/sqrt(2);
		z:=(1+z*(.0705230784+z*(.0422820123+z*(.0092705272+
		      z*(.0001520143+z*(.0002765672+z* .0000430638))))))**(-16);

		PHI:=if x>=0 then 1-z/2 else z/2

	end PHI;