As a general guide book for writing a very useful text is
Best Books for Writers | Poets and Writers
Effective Writing: A Handbook for Accountants, May & May
Dr. Picard recommends this book for writing-intensive, case-based courses in accounting; also a useful resource for any business major. Available in the ISU bookstore.
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Since this book was published, Cameron has written several others, but my feeling is that, as with most self-help series, the most powerful tools are in the introductory volume. For example, you can buy an "Artist's Way" blank book for writing morning pages, or you can just use any notebook or paper or your laptop.