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: OBJECTIVE : to analyze aspects of TEE safety associated to the use of Midazolan ( MZ ) and Flumazenil ( FL ) and the influence of the clinical variables on the event rate .
### Output Text:
OBJECTIVE : to analyze aspects of TEE safety associated to the use of <span class="chemical">Midazolan</span> ( <span class="chemical">MZ</span> ) and <span class="chemical">Flumazenil</span> ( <span class="chemical">FL</span> ) and the influence of the clinical variables on the event rate . 