residuals (also called the generalised equation errors or GEEs) $\varepsilon(t_k)$, is minimised. The residuals are written as $$\begin{aligned}
    \varepsilon(t_k) :&= y(t_k)-\frac{B(p)}{A(p)}u(t_k) \notag \\
    \label{gee}
    &= A(p)y_f(t_k)-B(p)u_f(t_k),  
    \end{aligned}$$ where $$y_f(t_k) = \frac{1}{A(p)}y(t_k) \textnormal{, and } u_f(t_k) = \frac{1}{A(p)}u(t_k). \label{filt1}$$ Note that in and we have adopted a mixed notation of CT operators and DT data. Since this dichotomy is repeatedly encountered in this paper, we formalise it in the following remark.

**.** \[remark1\] In this paper, $G(p)x(t_k)$ means that the DT signal $x(t_k)$ is interpolated in some manner, e.g., using a ZOH or FOH, and the resultant output through the CT filter $G(p)$ is sampled at $t=t_k$. On the other hand, $\{G(p)x(t)\}_{t_k}$ (or $[G(p)x(t)]_{t_k}$ in the vector-valued case) means that the CT signal $x(t)$ is filtered through $G(p)$, and later sampled at $t=t_k$.

The SRIVC method is described in Algorithm \[algorithm1\], where we denote $\varphi_f(t_k)$ as the filtered regressor vector, $\hat{\varphi}_f(t_k)$ as the filtered instrument vector, and $y_f(t_k)$ as the filtered output. Note that line 8 of Algorithm \[algorithm1\] requires the DT signals to be prefiltered by CT transfer functions. This is usually done by assuming a ZOH or FOH reconstruction for the input and output signals and then simulating the 