I've been interested in the subject of metalanguages [in mathematical logic] and how (if) we can formalize them. Most metalanguages I've encountered use some variation of a natural language (such as English, German or French). Therefore, a relevant question is "how can we mathematically formalize natural languages" or at least, certain aspects of it. However, there are very few sources (As far as I've seen) that concern themselves with the subject. I've only seen two papers that have dealt with a similar subject, thus far; One from Richard Montague, and the other from Thomas Graf.
If you could kindly introduce me to references such as papers, books or any resources that deal with this subject itself and/or its prerequisites (such as syntax, semantics, formal languages), I'd be most thankful.
I'm an undergraduate mathematics student in my fourth semester; I'm not as familiar as I'd like to be in both logic and linguistics; So, even the most trivial resource would be most useful to me.
Thank you, very much.