Production 51 (Mixed)

In http://www.w3.org/TR/1998/REC-xml-19980210 
production 51 for Mixed content models allows both:

(#PCDATA)

and:

(#PCDATA)*

but the spec is silent as to whether these are equivalent or
not, and if not, what the difference between them is.  It would
be worth adding a sentence to clarify this point.