Pop-in phenomenon during nanoindentation in MgO C. Tromas, J. Colin, C. Coupeau, J. C. Girard, J. Woirgard and J. Grilhé Eur. Phys. J. AP, 8 2 (1999) 123-128 Published online: 15 September 1999 DOI: 10.1051/epjap:1999237