Labille, M.-C., Janousek, Z., Merenyi, R., Vermander, M., Viehe, H.-G., Tinant, B., & Declercq, J.-P. (1990). Synthesis and X-Ray analysis of spiro compounds from twofold [2+2] cycloaddition of ynamines to carbon suboxides. New Journal of Chemistry, 15, 79-83. https://hdl.handle.net/2078.5/84763 (Original work published 1990)