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: Severe and clinically evident anemia was easily corrected by subcutaneous injections ( 3 times / week for 1 month ) of recombinant erythropoietin ( rHuEPO - beta ) .
### Output Text:
Severe and clinically evident anemia was easily corrected by subcutaneous injections ( 3 times / week for 1 month ) of recombinant erythropoietin ( rHuEPO - beta ) . 