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: Histopathologically , typical findings were observed in the cerebella from the control groups , but the findings consistent with early embryonic development were noted in BCNU - exposed cortical dysplasia group .
### Output Text:
Histopathologically , typical findings were observed in the cerebella from the control groups , but the findings consistent with early embryonic development were noted in <span class="chemical">BCNU</span> - exposed cortical dysplasia group . 