\documentclass[lang=cn]{elegantbook}%based on v4.4

\begin{document}

 \[
    A=\begin{matrix}
        s_1 \\ s_2 \\ \vdots \\ s_t
      \end{matrix}
      \begin{pmatrix}
        A_{11} & A_{12} & \cdots & A_{1l} \\
        A_{21} & A_{22} & \cdots & A_{2l} \\
        \vdots & \vdots &        & \vdots \\
        A_{t1} & A_{t2} & \cdots & A_{tl}
      \end{pmatrix}
\]

\[
    \boldmath{A}=\begin{matrix}
        s_1 \\ s_2 \\ \vdots \\ s_t
            \end{matrix}
            \begin{pmatrix}
        A_{11} & A_{12} & \cdots & A_{1l} \\
        A_{21} & A_{22} & \cdots & A_{2l} \\
        \vdots & \vdots &        & \vdots \\
        A_{t1} & A_{t2} & \cdots & A_{tl}
            \end{pmatrix}
\]

\end{document}