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: A forty - six year - old premenopausal woman developed headache , nausea and vomiting , left hemiparesis and seizure two days after parenteral use of progesterone and estradiol .
### Output Text:
A forty - six year - old premenopausal woman developed headache , nausea and vomiting , left hemiparesis and seizure two days after parenteral use of <span class="chemical">progesterone</span> and <span class="chemical">estradiol</span> . 