Perfect verb tenses The Second World War (begin)had begun in 1939, and it (end)in 1945.

The Second World War had begun in 1939, and it had ended in 1945.

Explanation:

these are past perfect verb tenses of (begin) and (end)

The correct way to cite this in APA format is the following: Smith, D. (2001). World Environment Day. Retrieved from http://www.businesstraveler.com 
APA (American Psychological Association) style is most commonly used to cite sources within the social sciences. 
Quotation styles can differ by use and by styles and every subject has its own unique style of quotation.