APA (7th ed.) Citation
Van der Heijden, P., & ET AL. Methods for population size estimation of problem drug users using a single registration.
Chicago Style (17th ed.) Citation
Van der Heijden, P.G.M, and ET AL. Methods for Population Size Estimation of Problem Drug Users Using a Single Registration.
MLA (9th ed.) Citation
Van der Heijden, P.G.M, and ET AL. Methods for Population Size Estimation of Problem Drug Users Using a Single Registration.
Warning: These citations may not always be 100% accurate.