Penrose's paper: https://mathstat.dal.ca/~selinger/papers/papers/graphical-bib/public/Penrose-applications-of-negative-dimensional-tensors.pdf https://mathstat

Penrose's paper: https://mathstat.dal.ca/~selinger/papers/papers/graphical-bib/public/Penrose-applications-of-negative-dimensional-tensors.pdf https://mathstat.dal.ca/~selinger/papers/papers/graphical-bi...