how overrule tellurian stylesheet

in nutshell, there's tellurian stylesheet:

a { font-family: arial; }

i wish opposite arise family sole link:

<a href="..." style="font-family: helvetica;">...</a>

or

<span style="font-family: helvetica;"><a href="...">...</a></span>

but zero works. there an easy proceed this?

p.s. i'm boldly (via php) distribute opposite fonts opposite links, formulating special category an option.