"book-pflow-xyz/chapters/appendix-d-glossary.md" . . "An equation $\\mathbf{y}^T \\mathbf{C} = \\mathbf{0}$ where $\\mathbf{y}$ is a vector of weights and $\\mathbf{C}$ is the incidence matrix. Conservation laws prove that weighted sums of token counts remain constant across all firings. Example: in an SIR model, $S + I + R = N$ for all time."@en . . "Conservation law"@en .