J. A tale of contextuality... K. ...and its logical implications III. Mathematical proofs of contextuality A. The Kochen-Specker Bell theorem B. KCBS inequality C. Peres-Mermin Square IV. The graph-theoretic approach of Cabello, Severini and Winter (CSW) A. General definitions B. The case of KCBS as a paradigmatic example C. Generalisation D. Link with Bell inequalities V. A sheaf-category theoretic approach to contextuality A. Pictorial representation 1. Probabilistic contextuality 2. Logical contextuality 3. Strong contextuality B. A brief presentation of the mathematical frameworks of the model 1. Correlation experiments in sheaf-theoretic approach 2. Compatibility of marginals 3. Hierarchy of contextuality C. New questions D. An illustration of contextuality VI. A hypergrah approach to contextuality VII. An operational version of contextuality A. A toy model B. An operational theory of contextuality C. Application to quantum mechanics D. Reinterpretation of the Kochen-Specker results VIII. Contextuality-by-Default A.