What are special corporations?

\begin{tabular}{|l|c|c|} \hline & TAX RATES & TAX BASE \\ \hline DC & & \\ \hline Proprietary Educational Institution & 10% & Net Income \\ \hline Non- profit Hospitals & 10% & Net Income \\ \hline Govt. Educational Institution & & \\ \hline Domestic Carriers & 30% & Net Income \\ \hline Cemetery co. owned for the benefits of members & & \\ \hline RFC & & \\ \hline International Carriers & 2.5% & Gross Ph. Billings \\ \hline Resident Foreign Hospitals for profit & 30% & Net Income \\ \hline ROHQ & 10% & Net Income \\ \hline RHQ & & \\ \hline NRFC & & \\ \hline Nonresident owner/lessor of vessel & 4.5% & Gross Receipts \\ \hline" " cinematographic film owner/lessor & 25% & Gross Income \\ \hline " aircraft, machineries, other equipment & 7.5% & Gross Receipts \\ \hline \end{tabular}