I'm looking for a book or introductory article, that explains branching rules in representation theory of Lie groups. When a Lie group has a set of irreducible representations, I'd like to know how these representations decompose into irreducible representations of a subgroup. I heard of "Symmetry, representations, and invariants" by Goodman and Wallach and "Representation Theory" by Fulton and Harris, but I couldn't get an account on the special cases I'm interested in, which are $U(1) \to SU(2)$ and $SO(4) \to SO(5)$.