1. Check if the article is available in another library. Under the tab 'available at' in PiCarta you will find more information. You request the publication via Interlibrary Loan (ILL). This service is not free of charge.
2. Find out if the publication is available in a foreign library, for instance via Google Scholar or WorldCat. You order books from abroad via Interlibrary Loan (ILL).
3. Ask the author to send you the article. On publishers' sites and in search engines such as Scopus you will often find the email addresses of authors.
4. Twitter to the rescue: tweet your request together with the URL and add the hashtag #icanhazpdf