VATICAN CITY (AP) — Bolivian President Evo Morales has again raised eyebrows with an unusual gift for Pope Francis: books about the health benefits of coca leaves.

Morales met with Francis Friday before attending a Vatican conference on social and economic justice. U.S. Democratic presidential candidate Bernie Sanders is also among those attending.

During the audience, Morales presented Francis with three books: "Coca, a bio-bank," ''Coca, citogenic diet" and "Coca, the anti-obesity factor."

Morales sparked a minor diplomatic incident during Francis' 2015 visit to Bolivia by giving the pope a crucifix fashioned as a communist-style hammer and sickle. Francis said he wasn't offended.

Coca leaf, the raw material for cocaine, is widely chewed in the Andes to fight against altitude sickness and as a mild stimulant.