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: The majority of additional administration of oxytocics ( 4 / 5 ) and blood transfusion ( 3 / 5 ) occurred in the dose groups of 200 microg .
### Output Text:
The majority of additional administration of oxytocics ( 4 / 5 ) and blood transfusion ( 3 / 5 ) occurred in the dose groups of 200 microg . 