The notion of integrability can be extended to systems with boundaries. In large volume and finite temperature, the free energy of such systems – unlike those periodic – contains a non-extensive piece, called g-function, with many physical interpretations. We present a method [1906.07733] hybrid of [1003.5542, 1007.1148, 1809.05705] to calculate the g-function from the TBA partition function. NOTE: Thus is an online seminar using Zoom. Please follow the registration link on https://integrability-london.weebly.com/