The universality is remarkable, but yet to be described beyond phenomenological standard model of tunneling two-level systems.


## exclusively? [thermal conductivity is due to PHONONS!!!](https://knowen-production.s3.amazonaws.com/uploads/attachment/file/5382/PhysRevB.12.4475.pdf) Zaitlin-Anderson

## 1971 [Anomalous Low-temperature Thermal Properties of Glasses and Spin Glasses](https://knowen-production.s3.amazonaws.com/uploads/attachment/file/5394/14786437208229210.pdf) By P. w. ANDERSON, B. I. HALPERIN and c. M. VARMA

## 1987 Phillips [Two-level states in glasses](https://knowen-production.s3.amazonaws.com/uploads/attachment/file/5461/phillips%2B1987.pdf)

## [1971 - Zeller-Pohl](https://knowen-production.s3.amazonaws.com/uploads/attachment/file/5462/zeller-pohl.pdf)


## TOGETHER [linear-T specific heat and $ T^2$-thermal conductivity](https://knowen-production.s3.amazonaws.com/uploads/attachment/file/5383/Stephens-PRB73.pdf) Stephens

## [Freeman- Anderson](https://knowen-production.s3.amazonaws.com/uploads/attachment/file/5389/physrevb.34.5684.pdf) $150* \lambda = l$


## Graebner-1986 [Phonon localization in glasses](https://knowen-production.s3.amazonaws.com/uploads/attachment/file/5543/graebner.pdf)
J. E. Graebner, B. Golding, and L. C. Allen


## [PHONONS IN AMORPHOUS MATERIALS - review - S. Hunklinger](https://knowen-production.s3.amazonaws.com/uploads/attachment/file/5561/ajp-jphyscol198243C991.pdf)