Nolan, R., Usher, R. and Heron, N. 2019. An Overview of the Athlete’s Biological Passport (ABP) in Professional Road Cycling and causes of natural variation within the ABP. Journal of Science and Cycling. 8, 3 (Dec. 2019), 3-8. DOI:https://doi.org/10.28985/1920.jsc.02.