• For reviews of squaric acid and its derivatives, see: Synthesis, 1, 649, 869 (1978); 961 (1980). See also: J. Chem. Soc., Perkin 1, 263 (1993).
• Interesting dibasic acid, readily forming salts, acid chloride, esters, amides, etc. Esters of squaric acid have been used to synthesize chiral bioisosteres for the amino acid functionality: J. Org. Chem., 57, 6896 (1992).