Madhav Nori invented an original approach to mixed motives, in the spirit of Tannakian theory, but based on a specific Nori's Tannakian theorem. Unfortunately his original work, which has been lectured on some summer schools and conferences is not widely available in written form. Maxim Kontsevich based his approach to periods and their appearance in deformation quantization partly on Nori’s insight.
Annette Huber, Stefan Müller-Stach, On the relation between Nori motives and Kontsevich periods, 1105.0865
Madhav Nori, TIFR notes on motives, unpublished, pdf
Jonas von Wangenheim, Nori-Motive und Tannaka-Theorie, arxiv/1111.5146
J. Ayoub, L. Barbieri-Viale, Nori 1-motives (arXiv:1206.5923)