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: The aim of our study was to demonstrate the perioperative course of thrombocytopenia after liver transplantation and determine the occurrence of clinical HIT type II .
### Output Text:
The aim of our study was to demonstrate the perioperative course of thrombocytopenia after liver transplantation and determine the occurrence of clinical HIT type II . 