How to create Dart language spec pdf/epub

Dart site does not provide pdf document of Dart language specification.

 https://www.dartlang.org/docs/dart-up-and-running/contents/ch02.html

I don't understand the reason, but it is definitely inconvenient.

So I created pdf/epub on linux(Ubuntu)

[pdf creation]

http://www.cyberciti.biz/open-source/html-to-pdf-freeware-linux-osx-windows-software/

$ sudo apt-get install wkhtmltopdf
$ sudo ln -s /usr/bin/wkhtmltopdf /usr/local/bin/html2pdf

html2pdf https://www.dartlang.org/docs/spec/latest/dart-language-specification.html#h.5c9w1alpe7y datlang-spec-0.51.pdf

[epub]

$ sudo add-apt-repository ppa:n-muench/calibre
$ sudo apt-get update
$ sudo apt-get install calibre

save above url to local file with browser and name it as dartlang-spec-0.51.html.

$ ebook-convert dartlang-spec-0.51.html  dartlang-spec-0-51.epub