Evaluation of the functional gastrointestinal diseases concept from standpoints of Rome IV (2016) diagnostic criteria (review) - D. N. Andreyev; A. V. Zaborovsky; A. S. Trukhmanov; I. V. Mayev; V. T. Ivashkin (Российский журнал гастроэнтерологии, гепатологии, колопроктологии, 2018)