APA (7th ed.) Citation

Nielsen, J. (1950). A study concerning the congruence subgroups of the modular group. Munksgaard.

Chicago Style (17th ed.) Citation

Nielsen, Jakob. A Study Concerning the Congruence Subgroups of the Modular Group. København: Munksgaard, 1950.

MLA (9th ed.) Citation

Nielsen, Jakob. A Study Concerning the Congruence Subgroups of the Modular Group. Munksgaard, 1950.

Warning: These citations may not always be 100% accurate.