Scope of the article
David Art's book is mentioned in the article, so I think a good starting point should be what he wrote:  "In this book, I use "far right" as an umbrella term for any political party, voluntary association, or extraparliamentary movement that differentiates itself from the mainstream right...."Radical right" refers to a specific type of far right party that began to emerge in the late 1970s....[T]here has been a convergence around the term in the literature...." (Inside the Radical Right: The Development of Anti-Immigrant Parties in Western Europe (2011), p. 10)  He then says his definition draws from Betz (1994) and Mudde (2007).

My first comment is that since Art says there is convergence on use of the term we should not use in text attribution.  We should just acknowledge that while there is no consistency on terminology, the term normally refers to the wave of right-wing parties that began to emerge in the 1970s.  We should only  use in-text attribution when someone says something original.  For example Art refers to Betz when he provides Betz's explanation of why these parties are right-wing.

Second, we need to ensure that the article is about a specific topic, in this case the parties and groups that began to emerge in the late 70s, and include only comments about these parties where the author is clearly referring to them.  For example, some writers use the term radical right to refer to parties such as the BNP but not UKIP.  Other writers may not use the term radial right but may call them "third wave" of the Extreme Right Party family, as Mudde did in his 1996 article "The War of Words Defining the Extreme Right Party Family."  Incidentally we should have an article that family too.  It's definition is similar to Art's use of "far right", although that term is more usually used for the more right-wing of the Extreme Right Parties, such as the BNP.