[source: Acts of the Apostles: The New Daily Study Bible, p. 

AUTHOR OF ACTS ALWAYS BELIEVED TO BE LUKE, BUT IT NEVER ACTUALLY SAYS SO
Although the writer never says so, from the earliest times Luke has been held to 
be its writer.
[source: Acts of the Apostles: The New Daily Study Bible, p. 2]

NEW TESTAMENT MAKES ALMOST NO MENTION OF LUKE WHATSOEVER
About Luke, we really know very little; there are only three references to him 
in the New Testament - Colossians 4:14, Philemon 24 and 2 Timothy 4:11.
[source: Acts of the Apostles: The New Daily Study Bible, p. 2]