[1] https://academic.oup.com/geronj/article-abstract/46/1/P9/638...
[2] https://www.econstor.eu/handle/10419/234818
[1] https://academic.oup.com/geronj/article-abstract/46/1/P9/638...
[2] https://www.econstor.eu/handle/10419/234818