Леонид, артикль лишний и если во мн.числе, то "their"

Большое спасибо!

ok)

I don't know what he wrote before, but "in the original language" is also correct

There were typos in the previous translation By the way, is it correct to say "to read books in the original"?

Very correct and very common

You should post it as an alternative – it's a good version for the learners to see.

I knew that version but when checking I found it only in Russian dictionaries. Thank you.

Here it is in Cambridge: http://dictionary.cambridge.org/dictionary/english/original?q=in%20original&a=british#original_3__3

I didn't look up carefully

on native

ON NATIVE doesn't work