While studying a larger problem, I occured upon the question of which integers can be represented by the binary quartic form $$f(x,y)=xy(x^2+y^2)$$ with $x,y\in\mathbb Z$. The standard text An Introduction to the Theory of Numbers by Niven, Zuckerman and Montgomery has an excellent chapter on binary quadratic forms, but unfortunately does not go into cubic or quartic forms. A simple Google search on "binary quartic forms" returns multiple papers on the subject, but nothing containing a systematic discussion about it. Several other Number Theory books I've seen do not appear to go into the theory of binary quartic forms either.
Question. Where can I learn about binary quartic forms?
Note that although the form $f(x,y)$ mentioned above is one of the reasons I want to learn about this, the purpose of this question is not to ask for an answer to the specific question of which integers are represented by $f(x,y)$. A reference/link to any resource (e.g. a textbook) which contains a systematic discussion on the subject from which I can start learning would be most appreciated. Thanks in advance!
Please note that I am mainly looking for a reference for binary quartic forms (not quadratic!), over $\mathbb Z$ specifically--although I would be happy to look at references which also discuss forms more generally, and where this is only, say, one of the subsections.