2009 Andrew Gacek et al, "A two-level logic approach to reasoning about computations" arXiv
Associated with the latter logic are various notions of binding: for quantifiers within formulas, for eigenvariables within sequents, and for abstractions within terms.
2010 T. Csorgo et al, "Detailed L3 measurements of Bose-Einstein correlations and a region of anti-correlations in hadronic Z^0 decays at LEP" arXiv
The invariant relative momentum Q is identified as the eigenvariable of the measured correlation function.