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: Recorded were dose - limiting adverse events : hyper - or hypotension ( three ) , severe abdominal pain ( 0 ) , vomiting ( 0 ) and retained placenta ( four ) .
### Output Text:
Recorded were dose - limiting adverse events : hyper - or hypotension ( three ) , severe abdominal pain ( 0 ) , vomiting ( 0 ) and retained placenta ( four ) . 