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: Among users of third - generation progestagens , the risk of VTE was higher in users of desogestrel with 20 g ethinyloestradiol than in users of gestodene or desogestrel with 30 g ethinyloestradiol .
### Output Text:
Among users of third - generation <span class="chemical">progestagens</span> , the risk of VTE was higher in users of <span class="chemical">desogestrel</span> with 20 g <span class="chemical">ethinyloestradiol</span> than in users of <span class="chemical">gestodene</span> or <span class="chemical">desogestrel</span> with 30 g <span class="chemical">ethinyloestradiol</span> . 