Vitaku, E., D. T. Smith and J. T. Njardarson (2014). "Analysis of the Structural Diversity, Substitution Patterns, and Frequency of Nitrogen Heterocycles among U.S. FDA Approved Pharmaceuticals". Journal of Medicinal Chemistry. 57: 10257–10274. doi:10.1021/jm501100b. PMID25255204.{{cite journal}}: نگهداری یادکرد:نامهای متعدد:فهرست نویسندگان (link)
Vitaku, E., D. T. Smith and J. T. Njardarson (2014). "Analysis of the Structural Diversity, Substitution Patterns, and Frequency of Nitrogen Heterocycles among U.S. FDA Approved Pharmaceuticals". Journal of Medicinal Chemistry. 57: 10257–10274. doi:10.1021/jm501100b. PMID25255204.{{cite journal}}: نگهداری یادکرد:نامهای متعدد:فهرست نویسندگان (link)