Weisstein, Eric W., "{{{title}}}" ("{{{title2}}}") at MathWorld.
{{MathWorld2|title = title|urlname = urlname|title2 = title2|urlname2 = urlname2}}
where all four parameters must be in title case.
{{MathWorld2|title = Prime Number|urlname = PrimeNumber|title2 = Primes|urlname2 = Primes}}
{{MathWorld |title=Prime Number
|id=PrimeNumber |access-date={{subst:TODAY}}}}