"given a/the strong similarity of..."

I would like to ask you a question about the use of articles, which for non-bative speakers of English is quite problematic.

If I first discuss structures such as apple pie vs. apple cake, London Street vs. London Avenue, etc. and then write the following:

"According to AuthorX, given a/the strong similarity of such constructions, it might be an obvious choice to treat them equally as compounds, regardless of the phonological difference."

Should I use "a" or "the" article?