When it comes to finding synonyms for the phrase "touch upon", there's no shortage of options available. Some of the most commonly used alternatives include "mention briefly", "bring up", "refer to", "allude to", and "briefly discuss". Others prefer to use phrases like "outline", "sketch out", and "give a cursory mention". In more formal writing, you may see phrases like "touch on briefly", "touch on lightly", or "address briefly". Regardless of which synonym you choose, the key is to find a phrase that conveys the idea of briefly mentioning a topic, without delving too deeply into it.