Development and Validation of a Spectrophotometric Procedure for Determining Silicon in Common Horsetail (Equisetum arvense L.) Herb, Nikulin, Aleksandr Vladimirov, Potanina Olga Georgievna, Platonov Evgeniy Alexandrov, Bokov Dmitry Olegovich, Smyslova Olga Aleksandro, and Abramovich Rimma Aleksandro , Pharmacognosy Journal, September 2019, Volume 11, Issue 5, p.1124-1131, (2019)