Verb + 了 + 又 + Verb (again and again)

Looked, and looked, and looked

• Verb + (completed / change)了le + again又yòu + Verb = the same action repeated in the past.
• 看了又看kàn le yòu kàn = "looked again and again"; 想了又想xiǎng le yòu xiǎng = "thought it over and over".
• The doubled verb stresses persistence.

Verb + (completed / change)了le + again又yòu + (same) Verb

• Repeat the verb around (completed / change)了le…again又yòu to show it happened over and over.

he他tālook看kàn了leagain又yòulook看kàn。

• 看了又看kàn le yòu kàn = "looked at it again and again."

Recap

Read the full reference: HSK 5 grammar — Adverbs.