Example of a protocol from an observational study:
Wilcox, M. E., Lim, A. S., McAndrews, M. P., Wennberg, R. A., Pinto, R. L., Black, S. E., … Rubenfeld, G. D. (2017). A study protocol for an observational cohort investigating COGnitive outcomes and WELLness in survivors of critical illness: the COGWELL study. BMJ Open, 7(7), e015600. https://doi.org/10.1136/bmjopen-2016-015600