Licensee shall keep, and shall require that each Sublicensee keep, full, true and accurate books of account containing the particulars of its Net Sales and the calculation of royalties. Licensee and its Sublicensees shall each keep such books of account and the supporting data and other records at its principal place of business. Such books and records must be maintained available for examination in accordance with this Section 5.3.1 for * ( * ) calendar years after the end of the calendar year to which they pertain, and otherwise as reasonably required to comply with GAAP.