Quote Originally Posted by Antonio1986 View Post
For some reason I am confusing the words некоторый and the word какой-нибудь/то
For example:
1. This historical event is described in some books =
(a) это историческое событие описано в некоторых книгах
- I suppose that this implies that there are for example 10 books and the event is described in the 3 or 4 of them.
(b) это историческое событие описано в каких-нибудь книгах =
- The only thing I know here is that the event is descriped in some books but I don't have the slighest idea in how many.
I wrote a reply but it was lost due to site crash.

(a) Normally "некоторых" = "some of ..." that is a selection from some specified set is implied. "Существует много книг по этому периоду. В некоторых (из них) описано это событие."

(b) "это историческое событие описано в каких-нибудь книгах" = " I guess this event is described in some books (whatever thay are)." - But this usage is too specific. Much better "какие-нибудь" works in questions. "Описано ли это событие в каких-нибудь книгах? Да, оно описано в каких-то книгах." = "Do any books describe the event? Yes, some books do."