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: We have used a murine model of AIDS , infection of female C57BL / 6 mice with LP - BM5 murine leukaemia ( MuLV ) virus , to determine if AZT - induced anaemia is due , in part , to decreased responsiveness of erythropoietic precursors ( BFU - e ) to erythropoietin ( EPO ) .
### Output Text:
We have used a murine model of AIDS , infection of female C57BL / 6 mice with LP - BM5 murine leukaemia ( MuLV ) virus , to determine if <span class="chemical">AZT</span> - induced anaemia is due , in part , to decreased responsiveness of erythropoietic precursors ( BFU - e ) to erythropoietin ( EPO ) . 