In the sentence extracted from biomedical literature, identify all the chemical entities. The required answer format is the same sentence with HTML <span> tags to mark up specific entities. 
### Entity Markup Guides:
Use <span class="chemical"> to denote a chemical.

### Input Text: Oral thrush did not recur , but 60 % ( 3 / 5 ) of patients with hoarseness had recurrence .
### Output Text:
Oral thrush did not recur , but 60 % ( 3 / 5 ) of patients with hoarseness had recurrence . 