Source : Webster's Revised Unabridged Dictionary (1913)

Punctilious \Punc*til"ious\ (-y[u^]s), a. [Cf. It. puntiglioso,
   Sp. puntilloso.]
   Attentive to punctilio; very nice or exact in the forms of
   behavior, etiquette, or mutual intercourse; precise; exact in
   the smallest particulars. ``A punctilious observance of
   divine laws.'' --Rogers. ``Very punctilious copies of any
   letters.'' --The Nation.

         Punctilious in the simple and intelligible instances of
         common life.                             --I. Taylor.
   -- {Punc*til"ious*ly}, adv. -- {Punc*til"ious*ness}, n.

Source : WordNet®

punctiliously
     adv : in a punctilious manner; "he launched into a long history of
           the birth of communism, giving credit punctiliously to
           the work of Marx and Engels"