Algebras of invariants of forms that are complete intersections

The author lists all pairs $(n,r)$ such that the algebra of invariants of $n$-forms of degree $r$ is a complete intersection. Under the assumption $n\geqslant2$ and $r\geqslant3$, the pairs are $(2,3)$, $(2,4)$, $(2,5)$, $(2,6)$, $(3,3)$, $(4,3)$, and only these.
Bibliography: 12 titles.