Chellgren, B. ., Miller, A. ., & Creamer, T. . (2006). Evidence for polyproline II helical structure in short polyglutamine tracts. Journal of Molecular Biology, 361(2), 362-71. https://doi.org/10.1016/j.jmb.2006.06.044 (Original work published 2006)

Kelly, M. ., Chellgren, B. ., Rucker, A. ., Troutman, J. ., Fried, M. ., Miller, A. ., & Creamer, T. . (2001). Host-guest study of left-handed polyproline II helix formation. Biochemistry, 40(48), 14376-83. https://doi.org/10.1021/bi011043a (Original work published 2001)