With NATO leaders in Madrid inviting Poland, the Czech Republic, and Hungary to join the alliance, there is still controversy. This controversy concerns not only which countries should be invited to join now and in the future, but also whether NATO should be expanded at all.
"Trends. NATO Expansion: The Ins and the Outs of It,"
International Bulletin of Political Psychology: Vol. 2
, Article 5.
Available at: https://commons.erau.edu/ibpp/vol2/iss11/5