Greek handwriting | Handwritten Greek letters | How to handwrite in Greek
http://www.foundalis.com/lan/hw/grkhandw.htm
希腊字母大小写的笔画顺序各是什么?例如σ与Σ? - 知乎
https://www.zhihu.com/question/21222797/answer/91267948
怎么把各种希腊字母写得好看? - 知乎
https://www.zhihu.com/question/26413893/answer/32765465
国人最容易犯错的是σ和δ的运笔方向,不要搞错。