I have the Horst Linke book, Durbkat, so I know what the b. coccina looks like. It grows to 6cm long, that's like 2.4 inches or so, so it's not a big fish. I wouldn't know if there are smaller version of it out there, how much smaller do they want this fish to get? My book is from 1991, so a smaller species could have been discovered, but without reading the said article, again I wouldn't know. Why don't you try rereading the article or check the end of the article for a bibliography of some type. If this is a scholarly article, it should have a list of recommended sources or something like that, but don't go by what I say. I read a lot of scholarly journals and that is their standard practice, I don't know how your magazine operates.
If your so interested in bettas and anabantoids in general, I would recommend the above-mentioned book. It is a handy reference and has a great deal of information about numerous bettas species. It was selling for a very reasonable price at amazon when I bought mine.