(a) Each reviewer shall maintain all documentation necessary to establish that each review conformed to the review standards of the relevant review program, including the review working papers, copies of the review report, and any correspondence indicating the firm's concurrence, non-concurrence, and any proposed remedial actions and any related implementation.(b) The documents described in subsection (a) of this section shall be retained by the reviewer for a period of time corresponding to the retention period of the sponsoring organization, and upon request of the PROB, shall be made available. In no event shall the retention period be less than 120 days from the date of completion of the review by the sponsoring organization.