> as lemmas

1937 J. von Neumann Coll. Wks. (1962) IV. 208 A familiar symmetric gauge function is ϕ_p(u₁,..u_n = ∑ni=1 |u_i|^p^1/p for 1 ≤ p < + ∞.

1965 Pacific Jrnl. Math. 15 242 A function ϕ on a complex vector space is called a gauge function if ϕ(u) > 0 when u ≠ 0, ϕ(αu) = |α|ϕ(u) for complex α, ϕ(u + v) ≤ ϕ(u) + ϕ(v).