Tham khảo Rơi_tự_do

  1. ↑ Robert M. Martin (1997). Scientific Thinking. Publisher Broadview Press. ISBN 1551111306. Trang: 15-17.
  2. ↑ Peter Damerow. Exploring the Limits of Preclassical Mechanics: A Study of Conceptual Development in Early Modern Science: Free Fall and Compounded Motion in the Work of Descartes, Galileo and Beeckman. Publisher Springer, 2004. ISBN 038720573X. Trang 147.