Please, list here all the easily accessible and valuable particle physics articles you can find/remember. There are some very good ones that are pedagogical and easy to approach. I do not mean popular particle physics text. I mean publications and learning materials for undergraduate and graduate students in physics. For example, article that demonstrates group theory intuitively for particle physicist... PS. There are lots of articles in arxiv.org, but it is not very easy to find the best ones. Thanks.