You can find ISBN at http://www.worldcat.org/advancedsearch
Once you install the Zotero on your PC and Zotero add-on on the web browser, you can manage the references using Zotero.
When you find an important paper in the internet, you can store it by cricking "save to Zotero" button on your browser.
I store all reference papers in Dropbox to make it easy to access to them from various devices.
I set Mendeley to watch the local folder of the Dropbox in my note PC.
So, all reference papers are listed in my Mendeley account.
When writing a paper, "private group" function in the Mendeley is quite useful.
I make a group named "group 1" for the paper1 main text, and another group "goup1s" for the paper1 supplement, and an additional group "group1m" for the paper1 method section,
and put the references for paper1 main, paper1 suppl. and paper1 method to the corresponding groups.
Because Mendeley can make the bibtex entries for the selected papers,
we can make the bibtex entry for paper1 main, paper1 suppl. and paper1 method by selecting the all references in the groups and right click, then select "copy as bibtex entry".
To make the private group more than 5, payment is reqired.
I decided to pay for minimum cost plan which allows me to make 1000 private groups.