On December 5, 2006, the National Security Agency released a message from a [redacted] Communications Station to the Director of the National Security Agency.

https://www.nsa.gov/Portals/70/documents/news-features/declassified-documents/uss-liberty/field-unit-messages/station-has-voice-tapes.pdf

In that message the NSA admits to the existence of voice tapes of Sixth Fleet activity on June 8th involving the USS Liberty.

To date the NSA has refused to release those tapes.

With this letter you will be asking your Congressional Delegation to contact the NSA and ask them to release the tapes referred to in their message.