Isomerization of conjugated double bond

Recently found an interesting reaction which isomerized the conjugated double bond by the following sequence:
1. ketalize the ketone by acid/ethylene glycol. during which rxn the double bond isomerized to the more substituted position.
2. remove the ketal by oxalic acid which is efficient and mild enough to keep the double bond from isomerization to the more stable conjugated position.

very cool transformations, which demonstrated the author's deep understanding of those reagents and the beauty of organic transformations.
the paper was published about 30-40 years ago in jacs.