(b) All working drawings and specifications prepared by a licensee shall be signed and stamped with the licensee's seal: Provided, That nothing contained in this article shall be construed to permit the seal of a landscape architect to serve as a substitute for the seal of an architect, an engineer or a professional surveyor whenever the seal of such architect, engineer or professional surveyor is required by law.
(c) It is unlawful for a person who is not licensed under the provisions of this article to affix a seal on a document.