Many researchers have guessed at the reason, but a recent study finally offers solid clues. (scientificamerican.com)
The largest study yet of the most energetic particles to slam into Earth provides the first solid clues to where the particles come from. (sciencenews.org)
Between the facts that (1) the offensively unprofessional self - published books generally have low discoverability, and (2) there are usually plenty of solid clues to discern the better books from the worse ones, I think the risks of buying bad self - published books are low, if you take simple precautions. (mikespinak.com)