2007   October:  "Prove it with Swahili."  Illinois Council of Teachers of Mathematics Annual Meeting, Peoria, Illinois.

2006      April:  "The Way Back from Everywhere."  National Council of Teachers of Mathematics Annual Meeting, St. Louis, Missouri

2004     April:   " The Road Coloring Conjecture."   Albion College Mathematics Colloquium, Albion, Michigan.

2002
            October: "Eight, Nine, Small Arm Bone:  Counting on Your Body in Papua New Guinea." Illinois Council of Teachers of Mathematics, Peoria, Illinois.

            October:  "A Millennium Mathematics Prize Problem that Kids can Understand."  Illinois  Council of Teachers of Mathematics, Peoria, Illinois. (invited reprise)

2001
            March:  "A Millennium Mathematics Prize Problem for Kids."  44th Annual Conference
on the Teaching of Mathematics, Charleston, Illinois.

            October:  "A Millennium Mathematics Prize Problem that Kids can Understand."  Illinois  Council of Teachers of Mathematics, Peoria, Illinois.
 

2000   April:  "A Sampler of Ancient Mathematical Texts."  Pi Mu Epsilon Induction Ceremony
          and Dinner. Decatur, Illinois

          October:  "From All Sides, A Circle of Stones for Posterity."  Illinois Council of
          Teachers Annual Meeting, Springfield, Illinois.

1999

        April:  "The Universal Translator."  Distinguished Faculty Lecture, Millikin University
        Honors Convocation.  Decatur, Illinois.

        October:  "A Computer in the Test Tube: The Power of DNA Computing."
        Illinois Council of Teachers of Mathematics Annual Meeting. Springfield, Illinois.

1998
        October: "DNA, Kolams, and Transparent Letters: The Joys of Formal Grammars."
        Illinois Council of Teachers of Mathematics Annual Meeting. Springfield, Illinois.

1996
            April: "Warlpiri Ethnoalgebra." National Council of Teachers of Mathematics, Annual Meeting.
            San Diego, California.

October: "Formal Languages of Warlpiri Iconography." National Council of Teachers of Mathematics, Central Regional Meeting. South Bend, Indiana.

1995

October: "Ethnomathematics and Education." International Third World Studies Conference. Omaha, Nebraska.

1993

April: "Using Writing to Teach Mathematics." Invited address. Illinois Mathematical Association of Two-Year Colleges, Annual Meeting. Monticello, Illinois.

1992

October: "Using Line Segments to Depict Syllogisms." Illinois State Academy of Sciences, Annual Meeting. Carbondale, Illinois.

1990

April: "Natural Language and Unnatural Language." Illinois Section of the Mathematical Association of America, Annual Meeting. Decatur, Illinois.

1988

October: "Machine Translation with Two-Level Grammars." Illinois State Academy of Sciences, Annual Meeting. Peoria, Illinois.