APA (7th ed.) Citation

Halim, S., & Halim, F. (2020). Competitive programming 4: The lower bound of programming contests in the 2020s. Ingram content group.

Chicago Style (17th ed.) Citation

Halim, Steven, and Felix Halim. Competitive Programming 4: The Lower Bound of Programming Contests in the 2020s. United States, UK: Ingram content group, 2020.

MLA (8th ed.) Citation

Halim, Steven, and Felix Halim. Competitive Programming 4: The Lower Bound of Programming Contests in the 2020s. Ingram content group, 2020.