Gustafson spent most of his career at the University of Colorado, Boulder, in the Department of Mathematics.
[4] He returned to this topic in 2012 with a book exploring how the theory applies in the contexts of numerical analysis, wavelets, statistics, quantum mechanics, finance and optimization.
[5] Gustafson wrote an introductory guide to partial differential equations (Introduction to Partial Differential Equations and Hilbert Space Methods) that was published in three editions in the United States[6][7][8] and in various versions in three foreign countries.
[9][10][11] Gustafson also published academic books in other areas of mathematics[12] and in related subjects such as quantum mechanics[13] and fluid dynamics.
[17][18] Gustafson published a memoir in 2012, entitled The Crossing of Heaven, which recounted, among other life experiences, more of his mountaineering adventures and his role in top-secret (at the time) military intelligence work during the Cold War, including writing the software in 1960 for the first US spy satellite.