Can I Mix Multiple Nameserver Sources in resolv.conf

In the list of nameservers in resolv.conf, can I use different nameservers (one from ISP, one from Google, etc..) in each line or does it all have to be from same source?

Example:

nameserver 123.12.12.123   <-- ISP
nameserver 8.8.8.8 <-- Google
nameserver 75.127.14.107 <--- OpenNIC

Is mixing the nameserver sources normal or is it advisable to stick to only 1 source with 2 or 3 ip addresses from them?

I am asking this cuz all docs and examples I've seen only shows ip addresses from 1 source either Google, ISP, or other third-parties. I havent seen 1 that has mixed nameservers and wondering if that's normal.