Dear Mr. S:

You wrote:

 You recommend use of periods after the abbreviations, but that is completely opposite of Chicago Manual of Style, Microsoft Manual of style, and many other manuals.

Thank you for the note. This is something that is changing. We put this together nearly 20 years ago, and most sources in North America still recommended periods except for metric measurements and obvious acronyms.

It may be necessary for us to qualify our recommendations. As with other issues where not all authorities agree, whichever way you choose, be consistent.