Related Clues:

• Study (with "on")
• Go deep into
• Burrow
• Use a spade
• Research deeply
• Research
• Study, with 'on'
• Probe, with 'into'
• Study, with ''on''
• ___ on (study)
• Investigate (with ''into'')
• Rummage
• Go (into)
• Search, with "into"
• Investigate deeply (with ''into'')