[dlang library documentation] Why there are dlang.org/library and dlang.org/phobos?

[Johann]

It seems that std library documentation lives in two different 
directories.

https://dlang.org/phobos/

https://dlang.org/library/

Maybe it's due to historical reasons. Problem is, when I search 
for a library function in Google, sometimes it points me to 
library directory, and sometimes it points me to phobos directory.

In fact, when I search "dlang writef", it shows me two urls most 
relevant.

1. https://dlang.org/library/std/stdio/writef.html

2. https://dlang.org/phobos/std_stdio.html

Clicking "format string" hyperlink on first url gives a 404 
error. 
https://dlang.org/library/std/stdio/std_format.html#format-string

The second url is correct. 
https://dlang.org/phobos/std_format.html#format-string

Is https://dlang.org/library/ deprecated? If so, is it possible 
to remove it so that it won't confuse noobs like me?

Or if both directories are intented to be used, I'll file a bug 
instead.