Cover picture: Satellite tobacco mosaic virus (STMV) is one of the smallest viruses known. Its capsid contains 60 icosahedrally arranged identical protein subunits. Normal modes of capsid vibration resemble vector spherical harmonic functions and can be classified according to the icosahedral symmetry group. The layout and color scheme of this figure follow the artwork "Che Guevara" by Andy Warhol. See the article by Yang, Bahar, and Widom on page 4438.