For The Love Of Port

I am studying for an exam and need help. Can anybody provide a source for official and verifiable data about ABV and RS levels in madeira? There is a lot of vague and varied information online. Are RS levels fixed or is classification by style? Any help would be greatly appreciated.

I believe residual sugar is by style, not variety.
Extra Dry is equal or less than 49.1 gm/l.
Dry is equal or less than 59.3.
Medium Dry is between 54.2 and 78.1.
Medium Sweet is between 78.1 and 100.01.
Sweet is equal or above 100.01.

These numbers come from the IVBAM.

Thanks, Eric. Do you have RS numbers for frasquiera wines as well? I believe they are classified by style without rigid RS ranges but would love to know otherwise.

I'm going to assume these hold for frasquiera wines as well based on style.