► Wordpress child theme codex
https://codex.wordpress.org/Child_Themes

► How to Modify your Responsive Ad Code

https://support.google.com/adsense/answer/6307124?hl=en

► Drop-down menu obscures ad
https://support.google.com/adsense/answer/4533983?hl=en

► Adsense Ads limit
https://www.searchenginejournal.com/google-removes-adsense-ad-limit-policy-reasons-behind-change/171597/