Romàn found this a while ago, thought it would be good to post. If you use internet searches to look for scientific papers, rather than going via the library webpage, you often find the journal webpage wants to charge you, even when you know NUS subscribes. The slow way to deal with this is to go to the library webpage, find the journal, log in, search for the volume and page number, precious minutes of your life you will never see again.
Well no longer! Follow the instructions here and all you need to do is to click on a bookmark on firefox (or whatever browser you use, although firefox really is the best) et voilà! Journal realises you’re at NUS and gives you the article.