To cite SUNDIALS in publications use:

Hindmarsh AC, Brown PN, Grant KE, Lee SL, Serban R, Shumaker DE, Woodward CS (2005). “SUNDIALS: Suite of nonlinear and differential/algebraic equation solvers.” ACM Transactions on Mathematical Software (TOMS), 31(3), 363–396.

Corresponding BibTeX entry:

  @Article{,
    title = {SUNDIALS: Suite of nonlinear and differential/algebraic
      equation solvers},
    author = {A. C. Hindmarsh and P. N. Brown and K. E. Grant and S. L.
      Lee and R. Serban and D. E. Shumaker and C. S. Woodward},
    journal = {ACM Transactions on Mathematical Software (TOMS)},
    year = {2005},
    volume = {31},
    number = {3},
    pages = {363--396},
    publisher = {ACM},
  }