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: EXPERIMENTAL DESIGN : Because of their widespread use , the hematologic toxicity following coadministration of dexrazoxane and these three structurally different DNA cleavage enhancers was investigated : Sensitivity of human and murine blood progenitor cells to etoposide , daunorubicin , and doxorubicin + / - dexrazoxane was determined in granulocyte - macrophage colony forming assays .
### Output Text:
EXPERIMENTAL DESIGN : Because of their widespread use , the hematologic toxicity following coadministration of <span class="chemical">dexrazoxane</span> and these three structurally different DNA cleavage enhancers was investigated : Sensitivity of human and murine blood progenitor cells to <span class="chemical">etoposide</span> , <span class="chemical">daunorubicin</span> , and <span class="chemical">doxorubicin</span> + / - <span class="chemical">dexrazoxane</span> was determined in granulocyte - macrophage colony forming assays . 