"3,3',4,4\u2032-Biphenyltetracarboxylic dianhydride; 4,4\u2032-Biphthalic dianhydride" . "BPDA" . . "BPDA" . . . . . . "[5,5\u2032-Bi-2-benzofuran]-1,1\u2032,3,3\u2032-tetrone" . . .