Moir, James published the artcileColor and chemical constitution. XX. Some residual problems, Related Products of benzofurans, the publication is Transactions of the Royal Society of South Africa (1926), 131-8, database is CAplus.

cf. C. A. 19, 988. Locations of absorption bands are given for a considerable number of naphtholphthaleins, azo dyes, hydrazones, S compounds, and miscellaneous organic compounds Com. α-naphtholphthalein was shown to consist chiefly of a white substance (I) together with a small quantity of a brown substance (II). Apparently I is mostly the p,p’-isomer, with a little o,p (as with com. phenolphthalein); II is the o,o’-isomer, m. 234°.

Transactions of the Royal Society of South Africa published new progress about 596-01-0. 596-01-0 belongs to benzofurans, auxiliary class Benzofuran,Naphthalene,Alcohol,Ester, name is 3,3-Bis(4-hydroxynaphthalen-1-yl)isobenzofuran-1(3H)-one, and the molecular formula is C28H18O4, Related Products of benzofurans.

Referemce:
https://en.wikipedia.org/wiki/Benzofuran,
Benzofuran | C8H6O – PubChem