Contracting warrants, at all levels above the micro-purchase threshold, must be requested by the HCA in writing and signed by the Senior Procurement Executive. Warrants may be accompanied by letters of appointment that may provide requirements for maintaining the warrant (e.g., maintaining current documentation for the FAR, DOLAR, and other guidance, and recurrent training). Copies of the appointment shall be maintained in the Division of Acquisition Management Services. Contracting officers must display the original warrant (and its limitations) in their workspace. A listing of current contracting officers may be available for review on the Internet at http://www.dol.gov/oasam/grants/prgms.htm. To modify a contracting officer's authority, the present appointment must be revoked and a new certificate issued.