Cooper, George (March 1977). "A Voluntary Tax? New Perspectives on Sophisticated Estate Tax Avoidance". Columbia Law Review. 77 (2): 161–247. doi:10.2307/1121996. JSTOR1121996.
Cooper, George (March 1977). "A Voluntary Tax? New Perspectives on Sophisticated Estate Tax Avoidance". Columbia Law Review. 77 (2): 161–247. doi:10.2307/1121996. JSTOR1121996.