As a major component of library services, information and reference services are constantly developing as is the library itself.
The earliest concept of modern reference work is usually traced to Samuel Swett Green’s 1876 paper entitled “Personal relation between libraries and readers” in which he advocated the importance of personal service and guidance to the library patron .
Over the following hundreds of years the concepts and practices of reference work have been expanded and have evolved significantly.
Based on Green’s ideas, Bopp and Bunge categorized the practices of reference services into three groups