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: In the group where anemia was prevented by rHuEPO treatment , growth delay was comparable with that of nonanemic controls ( 13 . 3 days ) .
### Output Text:
In the group where anemia was prevented by rHuEPO treatment , growth delay was comparable with that of nonanemic controls ( 13 . 3 days ) . 