Источники статистики, использованной в книге: 2018 Chatbot Statistics – All The Data You Need by Alex Debecker https://blog.ubisend.com/optimisechatbots/chatbot-statistics, Most popular global mobile messenger apps as of April 2018, based on number of monthly active users (in millions) https://www.statista.com/statistics/258749/most-popular-global-mobile-messenger-apps/.