@Unpublished{Jon93-Email,
    Author       = "Jones, R.",
    Year         = "1993",
    Title        = "{Little Problem, Solved by Otter}",
    Series       = "HOL mailing list",
    Number       = "http://lal.cs.byu.edu/lal/holdoc/info-hol/15xx/1572.html",
    Comment      = "TPTPRef"
}