More books on selling and marketing and business to business marketing
Citation guides (see Citation Styles and Guides) will help with articles and other standard sources, but you may not find examples or specific guidelines for business sources. Just use your best judgment based on the guidelines. Here's an example for a source like IBISWorld (without the correct indentation) in APA:
Publisher/Database as author. (Publication date). Title of report. Retrieved from URL
IBISWorld. (2014, November). Office furniture rental in the US. Retrieved from http://www.ibisworld.com/
For more help, I like the following guides (developed by librarians so you can trust them). They are all just examples and they may not necessarily all agree, so use what works best for you (and your instructor) and be consistent.