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: This study was designed to evaluate the alterations in offspring rat cerebellum induced by maternal exposure to carmustine - [ 1 , 3 - bis ( 2 - chloroethyl ) - 1 - nitrosoure ] ( BCNU ) and to investigate the effects of exogenous melatonin upon cerebellar BCNU - induced cortical dysplasia , using histological and biochemical analyses .
### Output Text:
This study was designed to evaluate the alterations in offspring rat cerebellum induced by maternal exposure to <span class="chemical">carmustine</span> - [ <span class="chemical">1 , 3 - bis ( 2 - chloroethyl ) - 1 - nitrosoure</span> ] ( <span class="chemical">BCNU</span> ) and to investigate the effects of exogenous <span class="chemical">melatonin</span> upon cerebellar <span class="chemical">BCNU</span> - induced cortical dysplasia , using histological and biochemical analyses . 