Lectures at conferences

• 1980, June 8-14, Oberwolfach, Germany, Boundary eigenvalue problems and special functions
• 1981, September 14-19, Innsbruck, Austria, Meeting of the Austrian Mathematical Society
• 1982, Essen, Germany, Conference on vector measures and integral representation of operators, and on functional analysis/Banach space geometry
• 1982, August 23-28, Wuerzburg, Germany, Equadiff 1982
• 1983, June 5-11, Oberwolfach, Germany, Special functions and differential equations in the complex domain
• 1983, August 1-6, Glasgow, Scotland, 2nd International workshop on multiparameter spectral theory
• 1984, September 17-22, Kaiserslautern, Germany, Meeting of the German Mathematical Society
• 1985, July 29-August 9, Calgary, Canada, 3rd International workshop on multiparameter spectral theory
• 1986, June 18-21, Ulm, Germany, Conference on ordinary differential equations
• 1986, June 30-July 4, Dundee, Scotland, Ninth Dundee conference on differential equations
• 1986, October 6-12, Bonn, Germany, Conference on multiparameter spectral theory
• 1988, July 5-8, Dundee, Scotland, Tenth Dundee conference on differential equations
• 1988, September 12-16, Capri, Italy, Third conference on real analysis and measure theory
• 1989, April 2-8, Oberwolfach, Germany, Ordinary differential equations in the complex domain and special functions
• 1989, August 15-25, Calgary, Canada, 4th International workshop on multiparameter spectral theory
• 1993, May 20-22, Kalamazoo, Michigan, International symposium on ordinary differential equations and applications
• 1997, June 18-22, Chattanooga, Tennessee, Real Analysis Summer Symposium
• 1997, July 31-August 5, Waterloo, Canada, Conference on Differential equations and Dynamical Systems
• 1998, June 23-27, Santa Barbara, California, Real Analysis Summer Symposium
• 2000, January 10-14, San Diego, California, Symposium on Asymptotics
• 2000, September 22-23, DeKalb, Illinois, Conference on Ordinary Differential Equations in Honor of Tony Zettl
• 2002, July 21-August 2, IMA Minneapolis, Minnesota, Special Functions in the Digital Age
• 2004, January 6-11, Phoenix, Arizona, Joint Mathematics Meeting
• 2004, October 23, AMS Sectional Meeting at Northwestern University, Evanston, Illinois, « Comparison of eigenvalue problems due to Feller, Krein and Atkinson »
• 2004, October 24, AMS Sectional Meeting at Northwestern University, Evanston, Illinois, «The coexistence problem for the Heun equation»
• 2005, April, Workshop on Sampling, Spectral theory and Their Applications at the University of West Georgia, Carrollton, Georgia, three one-hour presentations: «Introduction to the Theory of Hill's Equation», «The Coexistence Problem for Hill's Equation», «The Lengths of Stability and Instability Intervals of Hill's Equation»
• 2006, April 9, AMS Sectional Meeting at Notre Dames University, South Bend, Indiana, «Instability intervals for the Hill and Ince equations»
• 2006, June 14, 30th Summer Symposium in Real Analysis at the University of Northern Carolina in Asheville «Eigenvalue problems and Real Analysis»

Lectures at universities

• 1989, University of Triest, Italy, lecture « The equichordal problem»
• 1991, February 2, San Diego State University, California, lecture «On regularity of wavelets»
• 1993, April 6, University of Calgary, Canada, lecture «The regularity of wavelets»
• 1993, June 16, University of Essen, Germany, colloquium talk «Introduction to the theory of wavelets»
• 1993, June 23, 30 and July 7, University of Essen, Germany, three additional lectures «Introduction to the theory of wavelets»
• 1993, July 7, University of Ulm, Germany, colloquium talk «Wavelets with compact support»
• 1993, October 15, University of Milwaukee, Wisconsin, colloquium talk «Asymptotic regularity of compactly supported wavelets»
• 1994, May 13, University of Wisconsin-Madison, talk in the analysis seminar «The equichordal problem»
• 1994, July 12, University of Cottbus, Germany, colloquium talk «Indefinite eigenvalue problems»
• 1994, July 1-31, University of Cottbus, Germany, seven lectures «Introduction to the theory of wavelets»
• 1995, July 5, University of Essen, Germany, colloquium talk «Indefinite Sturm-Liouville problems»
• 1995, July 6, University of Essen, Germany, colloquium talk «Estimate of convergence radii for two-parameter Sturm-Liouville equations»
• 1995, September 1, University of Calgary, Canada, seminar talk «Growth rate of convergence radii for two-parameter Sturm-Liouville equations»
• 1998, November 12, University of Essen, Germany, seminar talk «Open problems on Sidon sets»
• 1998, November 19, University of Essen, Germany, seminar talk «Heine-Stieltjes polynomials»
• 1998, November 25, University of Essen, Germany, colloquium talk, «Dynamical systems and inverse limits»
• 1998, December 15, University of Stassbourg, France, seminar talk «Heine-Stieltjes polynomials»
• 1999, April 14, University of Calgary, Canada, colloquium talk «Convexity of the Lyapunov exponent»
• 1999, April 16, University of Calgary, Canada, seminar talk «Analytic eigencurves»
• 2000, March 31, University of Wisconsin-Milwaukee, colloquium talk «On a problem of Richard Askey»
• 2001, February 22, Marquette University, Wisconsin, colloquium talk «Some functional equations in statistics»
• 2002, November 15, University of Wisconsin-Milwaukee, colloquium talk «The Digital Library of Mathematical Functions Project»
• 2003, April 25, Northern Illinois University at DeKalb, colloquium talk «Asymptotic distribution of eigenvalues of matrix Sturm-Liouville problems»
• 2004, April 30, Northern Illinois University at DeKalb, colloquium talk «The coexistence problem for the Heun equation»
• 2004 August 5, University of Calgary, Canada, seminar talk, «The Lambert function, and a conjecture of Ramanujan»
• 2005, January 20, Ohio State University, Columbus, Ohio, Applied Mathematics Seminar, «Infinite tridiagonal matrices and their applications»