The files
  <Spectra>/include/LinAlg/TridiagEigen.h
  <Spectra>/include/LinAlg/UpperHessenbergEigen.h
were adapted from
  Eigen/src/Eigenvaleus/SelfAdjointEigenSolver.h
  Eigen/src/Eigenvaleus/EigenSolver.h
in the Eigen library (http://eigen.tuxfamily.org/).
The authors for these two files were Gael Guennebaud <gael.guennebaud@inria.fr>
and Jitse Niesen <jitse@maths.leeds.ac.uk>.

Other part of Spectra was written by Yixuan Qiu <yixuan.qiu@cos.name>.
