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: Eighty patients who were to receive CYA 50 mg / kg / d for four days as preparation for marrow grafting underwent a total of 84 transplants for aplastic anemia , Wiskott - Aldrich syndrome , or severe combined immunodeficiency syndrome .
### Output Text:
Eighty patients who were to receive <span class="chemical">CYA</span> 50 mg / kg / d for four days as preparation for marrow grafting underwent a total of 84 transplants for aplastic anemia , Wiskott - Aldrich syndrome , or severe combined immunodeficiency syndrome . 