 Eigenvalues and Schur Forms in the LAPACK Users' Guide

Official reference documentation: netlib.org/lapack/lug/node50.html and netlib.org/lapack/lug/node56.html . Cited sections: Eigenvalues, Eigenvectors and Schur Factorization; Eigenvalues, Eigenvectors and Generalized Schur Decomposition. These define real Schur blocks, homogeneous generalized eigenvalue pairs, infinite eigenvalues and the distinction between regular and singular pencils. Standalone qualified source card matches the existing LAPACK-reference-card convention; no personal authorship inferred from the generated-page footer.