Conditional Connectors

http://www.shertonenglish.com/resources/es/connectors/connectors-conditional.php

http://www.grammaring.com/if-even-if-only-if-as-long-as-provided-supposing-unless-but-for-if-necessary-if-so-in-case-etc

http://dictionary.cambridge.org/es/gramatica/gramatica-britanica/if-or-whether