What Section?
SDR, SIR, and SAR

What does the website say?
where $s_{target}$ is the true source, and $e_{interf}$, $e_{noise}$ and $e_{artif}$ are error terms for interference, noise, and added \text{artif}acts, respectively.

What SHOULD it say?
where $s_{target}$ is the true source, and $e_{interf}$, $e_{noise}$ and $e_{artif}$ are error terms for interference, noise, and added artifacts, respectively.