Carol Goodson suggests:
"***this may sound harsh, but one way would be to avoid answering
posts for which the answers could easily be found in a decent academic
library."
There are times when that would clearly be an appropriate response, but since--
as people have pointed out in the past--we have a wide range of correspondents,
not all of whom are academics and some of whom have limited access to such
libraries, I prefer to err on the side of generosity. I apologize in advance
to those it offends!
I have been gratified by the responses when I have had requests of my own,
even though I probably could have dug harder and deeper to find answers.
The responses here saved me time and effort!