My sons want to sell their inheritance, what should I do?

I was a poor farmer, and we worked hard on out little fields, me and my wife O-lan. We often starved and once even had to go south, in the days of famine. Then we came back, and worked even harder, saved our money, and bought the land off a rich local landowner, whose family ruined itself with drugs and women. I became rich, I sent my sons to school, and they married well. My wife died. My sons are doing very well. I lived with my sons for some time, but then moved back to live in my old house, I like being close to my land. I know I will die soon, and even bought a nice quality coffin for myself. I am not afraid. But my sons visited me and thought that I didn't hear, and talk about selling my land when I die, and dividing the money. I shouted at them, and they tried to humour me. They can't sell the land, no one can rob you off the land. They are going the way the old family is gone, selling the land. What should I do, how can I keep the land in my family after I am gone?