@article{Hartmann1989,
    author = "Hartmann, P.",
    title = "A uniform description of phenakite type structures as superstructures of beta-Si3N4",
    journal = "Zeitschrift fuer Kristallographie (1979-2010)",
    year = "1989",
    volume = "187",
    pages = "139-143",
    ASTM_id = "ZEKRDZ"
}