LAWRENCE SELLIN, retired international businessman and medical researcher, Veteran, US Army Reserve, @LawrenceSellin:

• Pakistan's role in the fall of Afghanistan

LANI ELLIOTT, Economist specializing in the economic and interdisciplinary study of instability and internal conflict at field, policy and strategic levels, Washington assignments covered East Asia, Africa, Latin America and the Middle East as well as functional areas such as refugees, counter-narcotics and energy sector reform:

• A history of US involvement in South Vietnam