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: In conclusion , octreotide induced gall stones are generally small , multiple , and cholesterol rich although , in common with spontaneous gall stone disease , at presentation some patients will have a blocked cystic duct and some gall stones containing calcium .
### Output Text:
In conclusion , <span class="chemical">octreotide</span> induced gall stones are generally small , multiple , and <span class="chemical">cholesterol</span> rich although , in common with spontaneous gall stone disease , at presentation some patients will have a blocked cystic duct and some gall stones containing <span class="chemical">calcium</span> . 