# Birkhoff averages and rotational invariant circles for area-preserving maps

> Research article (Physica D Nonlinear Phenomena, 2020) · cited 50× · AI/ML

**Wikidata**: [openalex:W2997646426](https://www.wikidata.org/wiki/openalex:W2997646426)  
**Source**: https://4ort.xyz/entity/birkhoff-averages-and-rotational-invariant-circles-for-area-preserving-maps