The Interdisciplinary Journal of Problem-based Learning (IJPBL) publishes articles of research, related to all aspects of implementing problem-based learning (PBL) in K–12 and post-secondary classrooms. https://docs.lib.purdue.edu/ijpbl/
How to Enhance Interdisciplinary Competence - Interdisciplinary Problem-Based Learning Versus Interdisciplinary Project-Based Learning by Mirjam Brassler and Jan Dettmers. https://docs.lib.purdue.edu/ijpbl/vol11/iss2/12
Summary: This is a broad study that compares the two pedagogies. It does an excellent job in defining both, as well as discussing the importance of broadening into, and including, other disciplines, The paper also emphasises the benefits of PBL for students.
The Interdisciplinary Journal of Problem-based Learning (IJPBL) publishes articles of research, related to all aspects of implementing problem-based learning (PBL) in K–12 and post-secondary classrooms. https://docs.lib.purdue.edu/ijpbl/
The book, Successfully Implementing Problem-Based Learning in Classrooms, Research in K-12 and Teacher Education, edited by Thomas Brush & John W. Saye, published by Purdue, 2017 is worth the price of admission.
Summary: Included in the first section of this book are studies regarding the topic from a perspective of pre-service teachers and where the support in teacher education classes are needed to support PBL learning in classrooms. The second half of the book goes in depth with studies and suggestions as to how practicing teachers can use PBL's in their classrooms. I highly recommend this book for summer reading. I read through it within two weeks, underlined a lot of it, and have shaped professional development opportunities to be offered in the near future.
The site: http://www.p21.org/ is a plethora of resources that can help acquaint oneself with the overarching concept of 21st century learning skills and what that looks like in learning environments. A fair warning - check this site out when you have some time to really explore the depth and breadth of this very informative site.