But if the Dentrassi let us on board, why doesn't the Guide mention them?

4 seconds sound clip from The Hitchhiker's Guide to the Galaxy (1981) - Episode 1 sitcom.

You can hear this line at 00:23:34.202 in the Blu-ray version of the TV Series.

Quote context

[...]

- Go on, have a bite. Go on, go on! Try it, try it. Your mouth will love you for the rest of your life.

- It's revolting!

- Oh, come on! This stuff is the greatest. Mmm!

- I think those guys must really hate the Vogons.

- Now, remember this. Dentrassi hate Vogons. That's why they let us on board. Let's go.

- But if the Dentrassi let us on board, why doesn't the Guide mention them?

- It's not very accurate. I'm researching the new edition.

(Vogon spaceship sliding door opening)

- Ah. Storeroom.

- Where are we going?

- Who knows? Off this ship, that's for sure.

[...]