A recent submission to Inv Prob Imag:
L. Roininen, S. Lasanen, M. Orispää and S. Särkkä: Sparse approximations of fractional Mat\'ern fields is available at http://arxiv.org/abs/1410.2113. Please note that this paper is not peer-reviewed. The paper has been submitted for peer-review process in Inverse Problems and Imaging.
Now, you may wonder why people want to make submissions before the paper has been accepted. There are several cons in this kind of situations, e.g. the paper may not qualify the peer-reviewing. However, if a paper has a significant breakthrough, it is important to get the paper public early. Especially this is the case when several persons are attacking a similar/same question, it is important that unofficial channels can be used, and hence to clearly demonstrate who was the original person making the claim/theorem/lemma. Hence, ArXiving by submission is typical in mathematics and similar fields. Hence, we emphasise that ArXiving upon submission is highly field-driven.