It's not hard but fun to get a glance at these different proof systems. But it's a pity that we didn't include the proof of Gödel's Incompleteness Theorems. \btw The proof systems are really ...
一些您可能无法访问的结果已被隐去。
显示无法访问的结果一些您可能无法访问的结果已被隐去。
显示无法访问的结果