Hi Selmer, 
Just wondering if you received the papers. If not, please let me 
know and I'll fax them to you tomorrow.
Here's a reference for Collatz's problem:
Gardner 1983] 
    Martin Gardner, Wheels, Life, and Other Mathematical Amusements. 
    W. H. Freeman. New York: 1983. Page 196. 

If you'd like more references, check out 

http://www.wwa.com/math/puzzles/unsolvedMathProblems/references.html

That document contains more than a dozen references to the problem.
Yrs,

Kostas