United States of America
http://www.irs.gov/uac/Eight-Tips-for-Deducting-Charitable-Contributions
England
http://www.hmrc.gov.uk/individuals/giving/gift-aid.htm
Australia
https://www.ato.gov.au/general/new-legislation/latest-news-on-tax-law-and-policy/
Austria
https://www.bmf.gv.at/steuern/selbststaendige-unternehmer/einkommensteuer/absetzbarkeit-spenden.html
Canada
http://www.cra-arc.gc.ca/chrts-gvng/dnrs/svngs/clmng1-eng.html
Hungary
http://www.nav.gov.hu/data/cms321491/13._sz._fuzet_Civil_szervezetek_20140220.pdf
http://net.jogtar.hu/jr/gen/hjegy_doc.cgi?docid=A1100175.TV
Donation contract certificate
Certificate for companies
Germany
https://www.smart-rechner.de/spenden/rechner.php
http://www.vlh.de/wissen-service/steuer-abc/was-sind-spenden-und-wie-setzt-man-sie-ab.html