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: Because of the clinical toxicities associated with chronic Urd administration , the ability of benzylacyclouridine ( BAU ) to effect , in vivo , AZT - induced anemia and leukopenia was assessed .
### Output Text:
Because of the clinical toxicities associated with chronic <span class="chemical">Urd</span> administration , the ability of <span class="chemical">benzylacyclouridine</span> ( <span class="chemical">BAU</span> ) to effect , in vivo , <span class="chemical">AZT</span> - induced anemia and leukopenia was assessed . 