Which of the following is classified as a non-official document?

Library reference materials are classified as non-official documents because they typically serve as general informational resources rather than authoritative or regulatory documents. These materials are often used for research, learning, or general guidance and do not carry the same official weight or obligation as official documents like regulations, meeting minutes, or contract agreements.

Meeting minutes are records of discussions and decisions made during formal meetings and are often considered official records. Printed regulations serve as formal guidelines or rules that are officially recognized and enforced within an organization or legal framework. Contract agreements are legally binding documents that outline the terms and conditions of a relationship between parties, making them official in nature. Consequently, library reference materials are categorized as non-official documents due to their non-binding and informational character.