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: Adverse events were reported in 68 . 9 % of patients ( myelosuppression in 49 . 4 % ) and 12 . 7 % of patients needed hospitalization .
### Output Text:
Adverse events were reported in 68 . 9 % of patients ( myelosuppression in 49 . 4 % ) and 12 . 7 % of patients needed hospitalization . 