Rights:
© 1996 American Physical Society (APS). This is the accepted version of the following article: Ruutu, J. P. & Hakonen, Pertti J. & Penttilä, J. S. & Babkin, A. V. & Saramäki, J. P. & Sonin, E. B. 1996. Evidence of 4He Crystallization via Quantum Tunneling at mK Temperatures. Physical Review Letters. Volume 77, Issue 12. 2514-2517. ISSN 0031-9007 (printed). DOI: 10.1103/physrevlett.77.2514, which has been published in final form at http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.77.2514.