Complex sentence: The Frontier Circle of the Archaeological Survey of India made detailed investigations of the site between 1960 and 1971; these were carried out by T.N. Khazanchi and his associates.
Split into simpler sentences: The Frontier Circle of the Archaeological Survey of India took up further detailed investigations of the site from 1960 and continued up to 1971. These investigations were carried out from 1960--71 by T.N. Khazanchi and his associates.