1,3-Cyclobutanedione, 2,4-bis(3,5-bis(1,1-dimethylethyl)-4-oxo-2,5-cyclohexadien-1-ylidene)- 2,4-Bis(3,5-bis(1,1-dimethylethyl)-4-oxo-2,5-cyclohexadien-1-ylidene)-1,3-cyclobutanedione 61377-20-6