Naturally aspirated is the default, so there isn’t really an “advantage”, that’s just how an engine operates.

So you probably would have an easier time finding disadvantages of forced induction techniques or whatever other options you’re considering in your class (alternate fuels, secondary fuels, maybe fuel delivery options) than you would finding advantages of the standard model.

If you’re specifically looking for performance optimization on naturally aspirated then try looking for increased compression ratio, reduced rotating resistance and mass, pumping losses, and timing as some of the keys there.

Does that help?

Naturally aspirated means no supercharger (blower) or turbocharger, unless you are talking about 2 stroke cycle Detroit Diesel engines that need a blower for normal operation and are considered naturally aspirated.
Superchargers (blowers) are driven by belt, driveshaft, or some direct drive means, and take a substantial amount of power from the engine. Turbochargers are driven by the exhaust gases escaping through the exhaust manifold, and take very little, if any, power from the engine.
All heavy-duty truck diesel engines sold after 1976 must have a turbocharger for increased high-altitude performance and emissions control.
Anytime you compress air, with blower or turbo, you cause the intake air to get hot. Cooling this air means more air can be forced into the combustion chamber for added power and better combustion. After cooling can be done with an air cooled radiator placed if front of the antifreeze radiator or with a antifreeze cooled radiator placed in the intake manifold of the engine.

The major advantage of “all motor, no blower” is simplicity and the resulting mechanical reliability; the fewer parts you have, the less that can go wrong.

That said, VW is going full turbo as a well-built turbo engine an get the power of a large engine with the MPG of a small one.

This book looks like a good place to start. An engineering textbook or peer-reviewed journal article is better than any website.

Youtube also has plenty of animations of internal combustion engines. I recommend this one for future directions (although it isn’t limited to N/A engines).

On a very basic level, the advantages of an N/A engine are simplicity, the potential for a higher rev limit, and higher compression ratios for similar engine stresses. Forced induction increases the pressure of the air entering the engine to above atmospheric pressure, while for an N/A engine this air will always be slightly less than atmospheric pressure. This means that forced induction engines have better efficiency, cleaner combustion, but lower compression ratios and rev limits – all else being equal. For example, 2013 N/A F1 engines rev to 18,000rpm, while the 2014 turbo engines will be limited to 15,000rpm. N/A engines also have superior throttle response. While modern forced induction engines are very good at reducing lag, it cannot be completely eliminated. A turbo or supercharger takes a moment of time to build intake pressure to the desired level, but since an N/A engine operates at normal atmospheric pressure, no such lag is present.

The other advantage of an N/A engine for a petrol-head like myself is sound. Turbochargers introduce turbulence into the exhaust stream, so the sound is not as clean. The supercharger whine can sound good, but is difficult to tune for acoustics. Compare this N/A sound to this turbo sound. The two cars both have high performance V8s with somewhat similar capacities, but to my ears the N/A Ferrari is more musical.