International Portage Conference Tokyo & Japan Portage Association. (1989). A challenge to potentiality: The vision of early intervention for developmentally delayed children : proceedings of the 1988 International Portage Conference in Tokyo, July 29-31, 1988. Japan Portage Association.

International Portage Conference Tokyo and Japan Portage Association. A Challenge to Potentiality: The Vision of Early Intervention for Developmentally Delayed Children : Proceedings of the 1988 International Portage Conference in Tokyo, July 29-31, 1988. [Tokyo: Japan Portage Association, 1989.

International Portage Conference Tokyo and Japan Portage Association. A Challenge to Potentiality: The Vision of Early Intervention for Developmentally Delayed Children : Proceedings of the 1988 International Portage Conference in Tokyo, July 29-31, 1988. Japan Portage Association, 1989.