These videos are made by Terry G4POP, and contains material about the free logprogram Log4OM Made by Daniele Pistollato – IW3HMH

Terrys videos are here:
https://www.youtube.com/channel/UC6Ppcj4Eb4-7QyavI-azOug

Here is a review by WB4IT:
http://wb4it.com/logging-software-log4om-review/

Here is some eHam.net reviews:
http://www.eham.net/reviews/detail/10506

If you want to check your logbook  for errors, Not only DXCC enity errors, But almost all sorts of errors in your log, Then you should make yourself a Clublog account, Its fast and easy. These guys have made a really good tool to help you out. After making an account, Upload your log in adif format, And you will recive a report via your email. Then fix the errors in your logbook if you got some.

Intro to Club Log:
http://clublog.freshdesk.com/support/solutions/articles/3000005477-introduction-to-club-log
http://clublog.freshdesk.com/support/solutions/articles/55695-determining-the-dxcc-country-entity-
http://clublog.freshdesk.com/support/articles/85385-check-your-upload-report

But Club Log has much more to offer, Why make an account and check it out.
https://secure.clublog.org/loginform.php

Club log