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: Two children with Wilms tumor of the left kidney experienced severe anthracycline cardiomyopathy after irradiation to the tumor bed and conventional dosage of doxorubicin .
### Output Text:
Two children with Wilms tumor of the left kidney experienced severe <span class="chemical">anthracycline</span> cardiomyopathy after irradiation to the tumor bed and conventional dosage of <span class="chemical">doxorubicin</span> . 