The Collaborative International Dictionary of English v.0.48:

Bis \Bis\, adv. [L. bis twice, for duis, fr. root of duo two.
   See Two, and cf. Bi-.]
   Twice; -- a word showing that something is, or is to be,
   repeated; as a passage of music, or an item in accounts.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Bis- \Bis-\, pref.
   A form of Bi-, sometimes used before s, c, or a vowel.
   [1913 Webster]

V.E.R.A. -- Virtual Entity of Relevant Acronyms (June 2006):

BIS
       Business Information System