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: Proximal tubular damage caused by HCBD and papillary damage caused by BEA were distinguished both by conventional urinalysis ( volume and specific gravity ) and by measurement of the two urinary enzymes .
### Output Text:
Proximal tubular damage caused by <span class="chemical">HCBD</span> and papillary damage caused by <span class="chemical">BEA</span> were distinguished both by conventional urinalysis ( volume and specific gravity ) and by measurement of the two urinary enzymes . 