Putra, G. A., Mulyantini, S., & Arieftiara, D. (2021). Business diversification of coal mining companies as a strategy facing coal price volatility: The effect on company performance and share prices. International Journal of Business Ecosystem & Strategy (2687-2293), 3(4), 38–50. https://doi.org/10.36096/ijbes.v3i4.299