3. expressing condition

(Transition words for different purposes)
a. coordinators: or else
b. paired subordinators: whether...or not 
c. subordinators: if / only if / unless / even if / whether / whether or not / provided (that) / in case / in the event (that)
d. transitions: otherwise / in the event (that) / anyway / anyhow  (referencehttp://www.grammar-quizzes.com/9-10.html)
(relevant: IV-D-e)

How to use IF & WHETHER properly
source: English Lessons with Adam    2015年7月31日

FCE LINKING WORDS (for conditional clauses and add information)
source: MrSkypelessons  2014年7月3日
Words such as 'unless, until, in case, furthermore, for instance' and many others are examined in terms of their meaning and function.
QUIZ: http://www.skype-lessons.com/blog/fce...

otherwise / or (else)
source: learnamericanenglish

3 ways to use 'as long as' 
source: English Lessons with Alex     2013年7月17日
quiz here: http://www.engvid.com/as-long-as/

How to use "unless"
source: Learn English with Rebecca      2013年7月10日
quiz: http://www.engvid.com/speaking-englis...

connectors that indicate condition (if so, if not, otherwise) or result (as a result, because of this, consequently, hence, therefore, thus
source: Your English Web        2016年8月26日