TITLE: Info about Elton–Odell theorem
QUESTION [5 upvotes]: Hello everyone, could anyone please tell me where can I find information about the Elton–Odell theorem?
It states:
For any infinite dimensional Banach space $X$ there is a $q > 1$ so that $X$ contains a sequence $(x_n)$ with $\|x_n\|=1$ and $\|x_n-x_m\|\ge q$, whenever $m\ne n$.
Thanks

REPLY [4 votes]: J. Diestel, Sequences and series in Banach spaces, Springer-Verlag, New York, 1984.
(Chapter XIV, page 241)