Open source code for Embedded Strong Discontinuity (EFEM)

Hi all,

I am now learning strain localization in solids and geometerial by
using Embedded Strong Discontinuity theory (EFEM or elemental
enrichment).  I am looking for an open source code to learn how to
understand and how to reproduce some examples by using EFEM. Did anyone
know that?

Any advice will be appreciated.

Cheers.