A proposed classification system was studied to determine its efficacy to the Air Force Control-Display Area. Based on negative outcomes from a logical assessment of the proposed system, an alternate system was proposed to include the coordinate index concept. Upon development of a thesaurus and an index system for 106 documents on VSTOL/VTOL aircraft, an experiment was conducted to determine the acceptance and effectiveness of the system on professional workers using the system. Findings revealed that the coordinate system was acceptable to the user and that it provided for the retrieval of relevant documents beyond that expected by chance. The study suggests that the coordinate index system and the present measures used to study its effectiveness provide a rationale for further experimentation which can expand the base of the system to meet the need of the control-display area. Appendixes include the proposed hierarchical classification scheme, the master word list and thesaurus, the posting index, a list of users, the tasks (questions), and the concepts used in searching. (Author/JB)