Zotero

Zotero.org: Open-source reference management software to manage bibliographic data and related research materials
Easy to add reference information (no manual typing) with browser connector.
Easy to cite references during writing with MS Word plubgin/Latex.
Can attach PDFs (any file). Free space up to 300 MB.
My Library vs Group Libraries: easy to share research papers among friends or with thesis advisor.
Group Library: RM-QF: papers to be covered in class are uploaded.
Can organize/classify papers by collections. One paper can belong to multiple collections.

Installation and Class Group Library

Install Zotero (Zotero for your OS + Browser Connector): Download
Create your account (free) and join the Group Library: RM-QF

Make sure to put your full name under profile

Creating reference list

Select all items (Ctrl-A).
Right-click. Select Create Bibliography from items....
Select China National Standard GB/T 7714-2015 (author-date, 中文). You'll have to download the GB/T style first.
Select either Bibliography or Citations. Select Copy to Clipboard
Paste into MS Word.

Zotero plug-in for MS Word (Complicated)

Install MS Word plugin: Edit - Preferences - Cite - Word Processors