Complex sentence: No known documents show that the Danite band operated at any time during its history under official LDS sanction, nor that the Danite band existed after Avard's excommunication and after 1838.
Split into simpler sentences: No known documents exist to prove that the Danite band operated at any time during its history under official LDS sanction. Likewise, no known documents exist proving the existence of the Danite band after Avard's excommunication and after 1838.