have you read this page on the use of arxiv which basically says it can be alright to use it as a source apart from that the papers mentioned in the 'in line notes and references' section have been published in peer reviewed journals but link to the arxiv version and of the arxiv links in the 'further reading' have also been published in journals also in a conference proceedings and also as a book of lecture notes this looks like potentially quite good sourcing to me whether the content of the article matches the information contained in the sources is another matter