Violet Errors, Oh, My!

Disclaimer time again!  I am not a botanist.  I recently posted photos of four kinds of violets, two yellow species, one white species, and one violet species.  I probably made some errors in identification, but get this:  The top photo, which I called Wood Violet, Viola lobata, is possibly Viola sheltonii, as one of my viewers suggested.  In the first field guide I consulted, V. sheltonii is called the Fan Violet, but is called Shelton's Violet in most other sources.  In my first field guide, V. lobata and V. sheltonii look very similar except for the color of the leaves and the number of lobes on each leaf.  The second photo above, I called the Pine Violet, Viola pinetorum.  Those are the names in the field guide I use most often.  I then found that most internet sites call V. pinetorum the Goosefoot Yellow Violet, and in one of the most popular field guides this species is absent.  To top it off, in that latter field guide, V. lobata is called the Pine Violet.  To make matters worse, when I type any one of these technical names into a browser and click on "images" I see photos of violets that are clearly of two or even three different species going by the same name.  So, to repeat my disclaimer, I am not a botanist, and I have not been able to untangle the conflicting descriptions I find in my several field guides.
I have found all the violets beautiful and fun to photograph, and, hopefully, my photos are sharp enough that you can click on each one for a close-up, examine the fine points and argue with your fellow nature lovers about which is which.  My 1951 Jepson Manual lists 20 species of violets in California, half of which are yellow.  Since it was published, there are either more or less than 20 species, depending on whether your favorite source is a lumper or a splitter.  Meanwhile, the violets just keep smiling back at us.  I'm more confident with reptiles and amphibians.