Specific EQN question

[Armando P. Stettner]

Hi Gang.
I am setting some mathematics using eqn and troff.  A second or square
root of an expression is simply specified by entering sqrt expression.
I have, however, an equation containing the third or cube roots of some
expression.  I do not want to raise this expression to a fractional
exponent (although I may have to).  Would somebody please send me mail
indicating whether or not it is possible to express this to eqn (and
if so, how).

I will summarize responses to the network.

Thanks.
	aps.