The Center for Latin American Studies welcomes John Messina for a Brown Bag Colloquium on "Alamos, Sonora: Recent Investigations" at 12:15 p.m. in the Douglass building, Room 102.

Leonid Friedlander speaks on "The Spectrum of Second Order Elliptic Operators in Periodic Waveguides" at 12:30 p.m. in the Math building, Room 402.

Tours of the fifth annual Tunnel of Oppression begin at Kaibab-Huachuca Residence Hall at 6:30 p.m. and continue until 9:30 p.m. Each tour lasts about a half hour. The tunnel will be open through Oct. 17.