Thanks, Mark, for reminder. I was talking about particular word "series". This word is a little bit tricky, since it looks like plural, but it is actually the same in both forms. I'm now wondering about other examples of such...

>Does this help?
>
>an article [one]
>the article [one]
>this article [one]
>these articles [more than one]
>the articles [more than one]
>
>
>>Hi everyone,
>>
>>I have a little bit of a problem today with my English grammar. In an article I'm proof-reading I see word series used as a single, e.g. with "a" article or with "this" article. I think, it should be changed to "the" and "these", but I started to feel uncertain about it.
>>
>>Would somebody please resolve this issue for me?
>>
>>Thanks a lot in advance.