https://www.google.fi/search?q=letter+to+the+editor,+cartoon&client=firefox-b&dcr=0&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjh5bWs7IvYAhViJpoKHR5TDGgQ_AUICigB&biw=1536&bih=758#imgrc=IUFyTz2KUaI-JM: (Dec 15, 2017)

Here are some tips:
https://prezi.com/t3wnropderpv/letter-to-the-editor/