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: CONCLUSIONS : Aerosolized crack cocaine use can be associated with the development of corneal ulcers .
### Output Text:
CONCLUSIONS : Aerosolized <span class="chemical">crack cocaine</span> use can be associated with the development of corneal ulcers . 