International Human Resources (hiring expatriates)

Explain the unique characteristic of human capital for the right fit for International Human Resources Management operations of hiring expatriates. Define the four ERPG Model of (1) ethnocentric, (2) geocentric, (3) polycentric, and (4) regio-centric/region-centric staffing approaches with the ability to adapt to different cultures in foreign environments. What are the strategies and challenges?