AKGUN, E., TUNALI, M. & PINDUR, U. (1987) THE REACTIONS OF ELECTRON-RICH HETEROCYCLES WITH DERIVATIVES OF ORTHOCARBOXYLIC ACIDS .8. PROTON ACID-CATALYZED ACYLATION OF INDOLES BY 2-ALKOXY-1,3-DIOXOLANES. ARCHIV DER PHARMAZIE , 320(5), 397-401.