The library holds a wide variety of books and ebooks on how to write business plans and concept statements. Use OneSearch with keywords such as "business plan" or "concept statement" and your product, market, or industry of interest.
San Jose Public Library maintains a large, current collection of business resources, including books on business plans. To check out their materials, either online or in print, you will need an SJPL library card. Most SJSU students are eligible for this card -- please see SJPL's website to apply for free card or e-card. Once you have that, you can check out their vast business collection.