A list of rules of keywords to avoid

[gdoron]

Hi,

I'm wondering if someone has a list of rules for keywords that won't work in Google Trends. For example:

1. A keyword cannot end with a dash(-) or else it will return status 400 ... ...

Thanks, Doron

[thatsthat]

The only info I found when looking at this was: "Special characters: Trends filters out queries with apostrophes and other special characters." Source: https://support.google.com/trends/answer/4365533?hl=en