UML各种图总结-精华 - 春风十里的情 - 博客园
https://www.cnblogs.com/jiangds/p/6596595.html
UML基础: 统一建模语言简介
https://www.ibm.com/developerworks/cn/rational/r-uml/index.html
UML图_百度百科
https://baike.baidu.com/item/UML图
Welcome To UML Web Site!
https://www.uml.org/
UML架构_w3cschool
https://www.w3cschool.cn/uml_tutorial/uml_tutorial-adei28ph.html
ProcessOn - 免费在线作图，思维导图，流程图，实时协作
https://www.processon.com/
推荐五个免费UML建模工具-百度经验
https://jingyan.baidu.com/article/6fb756ec75db3a241858fb07.html
UML图的Petri网建模_百度学术
https://xueshu.baidu.com/usercenter/paper/show?paperid=b7abdb288a2ae2f885b0a7be7a6003aa&tn=SE_baiduxueshu_c1gjeupa&ie=utf-8&site=baike