[nelson13]

I sometimes use CORPUS CONCORDANCE ENGLISH,
a concordancer, but why is a concordancer reliable?

Is the above one more reliable? Or is there any other way to see whether a modern sentence is correct?

[ICAL_Pete]

All things being equal a concordancer is only as reliable as the corpus it uses. A corpus could be British or American English only, or only scientific texts and so on. You need to make sure the corpus is suitable for what you are searching and then, assuming the software is well built, the results will be accurate.

[nelson13]

But sorry in the above link I can't find from where the texts have been taken.

Could anyone help me?

[ICAL_Pete]

Sorry, I don't understand what you mean. What are you looking for exactly?

[susan53]

A concordancer is simply a software programme which analyses a bank (or corpus) of authentic language data. Feed in any word or phrase and it will pull out all the examples of that word which are contained in the corpus or corpora that you are searching.
That means you see exactly how the word is really used in the language and not just how people think it is used (or even worse, how people think it should be used)- and that's why it's reliable.