Bid documents, depending on materials to be purchased, may vary. As a general practice, however, all bids as received from vendors shall be filled out in ink or by typewriter and they must be signed by an authorized representative. Unsigned bids will be rejected at the time of bid opening. Bids may include, but are not limited to the advertisement to the bid, the invitation to bid, the specifications and divisions thereof, instructions to bidders, general terms and conditions, special conditions, technical specifications, and any addenda issued thereto.