Porter, D. R., Phillips, P. L., & Lassar, T. J. (1988). Flexible zoning: How it works. Urban Land Institute.
Lua i Stíl Chicago (17ú heag.)Porter, Douglas R., Patrick L. Phillips, agus Terry J. Lassar. Flexible Zoning: How It Works. Washington, D.C: Urban Land Institute, 1988.
Lua MLA (9ú heag.)Porter, Douglas R., et al. Flexible Zoning: How It Works. Urban Land Institute, 1988.
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