Failed to start lightningd.service: Unit bitcoind.service not found

I followed the tutorial https://medium.com/@meeDamian/c-lightning-node-on-rbp3-b950660fb835 without error.
When I type:
sudo systemctl start lightningd
I get
Failed to start lightningd.service: Unit bitcoind.service not found.

Note: Blockchain syncronization is not finished

Any idea?
thank you