Government documents on microfiche are cataloged using the SuDoc classification system.
An explanation of the Superintendent Document classification system can be found at the Federal Depository Library Program website:
(Government microfiche use the same filing system as documents available in paper, so you will look for the microfiche in the same way.)
Many Government Documents are now available online. If you need help with any Government Documents, please feel free to contact the Government Documents Liaison, Sinai Wood.