To express 'than' with any comparative, use чљм.

Short:	Сђша умнље, чем Пљтя.	Sasha is more intelligent than Petya.
Long:	Сђша бћлее џмный человљк, чем Пљтя.	Sasha is a more intelligent person than Petya.

To express 'than' with short comparatives, you may also replace Nom./Acc with Genitive.

Short only:

Сђша умнље Пљти.

Sasha is more intelligent than Petya.

To express 'much more' or 'much less,' use горђздо. To express 'still more' or 'still less,' use ещё.

Сђша горђздо умнље.	Sasha is much more intelligent.
Сђша горђздо бћлее знђющий.	Sasha is much more knowledgeable.
Сђша ещё умнље.	Sasha is even more intelligent.