p can be embedded in a super-reflexive space X so that there is an operator $T\dvtx\ell_{p}\to\mathcal{C}(K)$ which has no extension, answering a question of Zippin.
@article{1242414132, author = {Kalton, N. J.}, title = {Automorphisms of $\mathcal{C}(K)$ -spaces and extension of linear operators}, journal = {Illinois J. Math.}, volume = {52}, number = {1}, year = {2008}, pages = { 279-317}, language = {en}, url = {http://dml.mathdoc.fr/item/1242414132} }
Kalton, N. J. Automorphisms of $\mathcal{C}(K)$ -spaces and extension of linear operators. Illinois J. Math., Tome 52 (2008) no. 1, pp. 279-317. http://gdmltest.u-ga.fr/item/1242414132/