O'Connor, J. S. (1987). A cross-sectional and longitudinal investigation of a physical activity classification system. [publisher not identified].
Chicago Style (17th ed.) CitationO'Connor, John S. A Cross-sectional and Longitudinal Investigation of a Physical Activity Classification System. [Place of publication not identified]: [publisher not identified], 1987.
MLA (9th ed.) CitationO'Connor, John S. A Cross-sectional and Longitudinal Investigation of a Physical Activity Classification System. [publisher not identified], 1987.
Warning: These citations may not always be 100% accurate.