Tài liệu tham khảo

WikiPedia: (181902)_1999_RD215 http://neo.jpl.nasa.gov/glossary/h.html http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=1999%20RD215 https://ssd.jpl.nasa.gov/horizons.cgi?find_body=1&... https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=181902#cont... https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=181902#disc... https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=181902#elem https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=181902#phys... https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=181902&orb=... https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=181902;cad=...