Observation of the strange sea in the proton via inclusive phi-meson production in neutral current deep inelastic scattering at HERA - Chekanov, S; Krakauer, D; Magill, S; Musgrave, V; Repond, J; Yoshida, R; Mattingly, M; Antonioli, P; Bari, G; Basile, M; Bellagamba, L; Boscherini, D; et al. (Physics Letters B, 2003)