- Letter to Certificate Holders: August 9, 2019 (PDF)
- Letter to Certificate Holders: February 9, 2017 (PDF)
- Letter to Certificate Holders: July 27, 2016 (PDF)
- Letter to Current 14(c) Certificate Holders Concerning the General Revocation Process: March 21, 2016 (PDF)
- Letter to Current 14(c) Certificate Holders Concerning Proposed Changes: August 21, 2015 (PDF)
- Letter to Certificate Holders: April 24, 2015 (PDF)