# Diophantine equations with egyptian fractions

I am looking for information about the following diophantine equation:
$\frac{1}{x_1} +\frac{1}{x_2} + \dots \frac{1}{x_k} = \frac{1}{n} \textrm{(k,n fixed)}$

Would it help if n has a special form (square, power of a prime number)?

I searched Google for egyptian fractions, didn't find anything really useful.

Thanks