Except as expressly provided to the contrary in this Agreement, every notice or other communication to be given by either party to the other with respect hereto shall be in writing and shall not be effective for any purpose unless the same shall be served personally or by national air courier service, or United States certified mail, return receipt requested, postage prepaid, addressed if to Licensee, at the address first set forth in this Agreement, and if to Licensor, at 999 - 18th Street, Suite 1201, Denver, Colorado 80202, or such other address or addresses as Licensee or Licensor may from time to time designate by notice given as above provided. Every notice or other communication hereunder shall be deemed to have been given as of the third (3rd) business day following the date of such mailing or immediately if personally delivered. Notices not sent in accordance with the foregoing shall be of no force or effect until received by the foregoing parties at such addresses required herein.