@book { AnImprovedLightweightPrivacyPreservingAuthenticationSchemeforSIPBasedVoIPUsingSmartCard,
    title = "An Improved Lightweight Privacy Preserving Authentication Scheme for SIP-Based-VoIP Using Smart Card",
    author = "Saeed Ullah {Jan}",
    year = "2017",
    publisher = "Anchor Academic Publishing",
    address = "Hamburg, Germany",
    url = "https://m.anchor-publishing.com/document/354819"
}