The article that pops into mind is an early one in the history of euglossine bee biology: Williams, N. H., and C. H. Dodson. 1972. Selective attraction of male euglossine bees to orchid floral fragrances and its importance in long distance pollen flow. Evolution 26: 84-95.
There may be others, but I am sure that they would have cited this one.
Thank you very much, Jim!! That is the kind of help that only great experts in orchid/orchid bee biology can provide so quickly!! I am sure this work will help a lot in my own work and will be easy to track other papers that cited this one. Research Gate is awesome!