@Article{LanguascoZaccagnini2010a,
  Author    = "A. Languasco and A. Zaccagnini",
  Title     = "On the constant in the {Mertens} product for arithmetic
               progressions. {I}. {Identities}",
  Journal   = "Functiones et Approximatio Commentarii Mathematici",
  Volume    = 42,
  Issue     = 1,
  Pages     = "17--27",
  Url       = "\url{http://it.arxiv.org/abs/0706.2807}",
  Year      = 2010,
  Abstract = "We give new identities for the constants in the Mertens
              product over primes in the arithmetic progressions
              $a \bmod q$, extending previous work by Uchiyama,
              Grosswald, Williams and Moree."
}