Петиция в поддержку Сергея Удальцова:https://www.change.org/p/%D0%B3%D0%B5%D0%BD%D0%B5%D1%80%D0%B0%D0%BB%D1%8C%D0%BD%D0%BE%D0%BC%D1%83-%D0%BF%D1%80%D0%BE%D0%BA%D1%83%D1%80%D0%BE%D1%80%D1%83-%D1%80%D1%84-%D1%8E-%D1%8F-%D1%87%D0%B0%D0%B9%D0%BA%D0%B5-%D1%81%D0%B2%D0%BE%D0%B1%D0%BE%D0%B4%D1%83-%D1%81%D0%B5%D1%80%D0%B3%D0%B5%D1%8E-%D1%83%D0%B4%D0%B0%D0%BB%D1%8C%D1%86%D0%BE%D0%B2%D1%83