Related Clues:

• Use a spade
• Research deeply
• Research
• Probe, with 'into'
• Do research
• Investigate (with ''into'')
• Rummage
• Go (into)
• Search, with "into"
• Search deeply (with ''into'')
• Do painstaking research
• Dig, as for information
• Search deeply (into)
• Look (into)
• Search deeply (with "into")