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 rapid systemic clearance of BCNU ( 1 , 3 - bis - ( 2 - chloroethyl ) - 1 - nitrosourea ) , intra - arterial administration should provide a substantial advantage over intravenous administration for the treatment of malignant gliomas .
### Output Text:
Because of the rapid systemic clearance of <span class="chemical">BCNU</span> ( <span class="chemical">1 , 3 - bis - ( 2 - chloroethyl ) - 1 - nitrosourea</span> ) , intra - arterial administration should provide a substantial advantage over intravenous administration for the treatment of malignant gliomas . 