In addition to its regularly scheduled monthly exhibits, River Gallery, 400 E. Second St., will present a side exhibit that features the collective work of Daud Akhriev (Spain), Melissa Hefferlin (Spain) and Mary Lynn Portera (Tennessee). The opening on Friday, March 28, includes a reception with the artists from 6:30 to 8 p.m. "Collaborations" will continue through Wednesday, April 30, coinciding with the gallery's March show, "Impressions," which ends Monday, March 31, and the April exhibit, "Nature at Its Best," which opens Tuesday, April 1. Regular hours are 10 a.m.-5 p.m. Monday-Saturday, 1-5 p.m. Sunday and by appointment. For more information, 423-265-5033, ext. 5, or visit www.river-gallery.com.