Hogan, P. (1974). Playgrounds for free: The utilization of used and surples materials in playground construction. MIT press.
शिकागो स्टाइल उद्धरणHogan, Paul. Playgrounds for Free: The Utilization of Used and Surples Materials in Playground Construction. Cambridge: MIT press, 1974.
एमएलए उद्धरणHogan, Paul. Playgrounds for Free: The Utilization of Used and Surples Materials in Playground Construction. MIT press, 1974.
चेतावनी: ये उद्धरण हमेशा 100% सटीक नहीं हो सकते हैं.