  \textit{Propus} (which means twins) is a construction method for orthogonal
$\pm 1$ matrices based on a variation of the Williamson array called the
\textit{propus array}
  \[ \begin{matrix*}[r]
  A& B & B & D
  B& D & -A &-B
  B& -A & -D & B
  D& -B & B &-A.
  \end{matrix*} \]
  This construction designed to find symmetric Hadamard matrices was originally
based on circulant symmetric $\pm 1$ matrices, called \textit{propus matrices}.
We also give another construction based on symmetric Williamson-type matrices.
  We give constructions to find symmetric propus-Hadamard matrices for 57
orders $4n$, $n < 200$ odd.
  We give variations of the above array to allow for more general matrices than
symmetric Williamson propus matrices. One such is the \textit{ Generalized
Propus Array (GP)}.
