Hi Jiří, yes, in the singular you should use an article: "such a literary work as..." or "such a nice day as this", for example. There is no article in the plural, for example: "such literary works as these".

The answer depends upon how you think of the noun. Let's use "pleasure" as an example. If you think of "pleasure" as something that can be enumerated then you say "such a pleasure" or "such pleasures". If you choose to think of "pleasure" as something that cannot be enumerated then you must say "such pleasure ".