Chi-squared distribution - Wikipedia

Noncentral chi-squared distribution - Wikipedia

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How can we use the chi-squared test in research? - Quora

Inverse-chi-squared distribution - Wikipedia

An Introduction to the Chi-Square Distribution

Noncentral Chi-Squared Distribution

Generalized chi-squared distribution - Wikipedia

Generalized chi-squared distribution - Wikipedia

Proofs related to chi-squared distribution - Wikipedia

10.2 The Chi Square Distribution – Introduction to Statistics

Let X1, X2, and X3 be independent random variables with standard normal distribution. What is the density function of Y =X1^2+X2^2+X3^2? - Quora

Chi Distribution -- from Wolfram MathWorld

Chi-square distribution - Distribuição Qui-Quadrado