The materials here are mostly out of print and are public domains which can be found in the world wide web. It’s just that you need to sacrifice your precious time and spend some hours to do some search on Google, Yahoo, Bing, Ask, DuckDuckGo, Baidu and numerous major search engine. All this materials are FREE in the World Wide Web ( www. the Internet ) albeit the accompanying malicious code or malware. It's also available in the vast popular YouTube, Facebook, WhatsApp, Instagram, WeChat, TikTok, Facebook Messenger, Telegram, etc. It's just merely a search and a sacrifice of time towards the separation of the overwhelming tons of unworthy ones from the beneficial ones. And it's of course, they are always free to obtain.