Behind this week's exercise in buttering-up and scolding is a broader tension in the two countries' approaches to one another. The new friends know that they are also rivals.

University of Groningen. "Making solar cells is like buttering bread." ScienceDaily. ScienceDaily, 21 March 2019. <www.sciencedaily.com / releases / 2019 / 03 / 190321130350.htm>.