The analysis and geometry of Hardy's inequality AA Balinsky, WD Evans, RT Lewis Springer, 2015 | 153 | 2015 |

Spectral analysis of second order difference equations DB Hinton, RT Lewis Journal of Mathematical Analysis and Applications 63 (2), 421-438, 1978 | 119 | 1978 |

The effect of variable change on oscillation and disconjugacy criteria with applications to spectral theory and asymptotic theory CD Ahlbrandt, DB Hinton, RT Lewis Journal of Mathematical Analysis and Applications 81 (1), 234-277, 1981 | 79 | 1981 |

Oscillation theory for generalized second-order differential equations DB Hinton, RT Lewis The Rocky Mountain Journal of Mathematics 10 (4), 751-766, 1980 | 66 | 1980 |

A minimax principle for eigenvalues in spectral gaps: Dirac operators with Coulomb potentials M Griesemer, RT Lewis, H Siedentop Doc. Math 4, 275-283, 1999 | 52 | 1999 |

Discrete spectra criteria for singular differential operators with middle terms DB Hinton, RT Lewis Mathematical Proceedings of the Cambridge Philosophical Society 77 (2), 337-347, 1975 | 51 | 1975 |

Singular elliptic operators of second order with purely discrete spectra RT Lewis Transactions of the American Mathematical Society 271 (2), 653-666, 1982 | 49 | 1982 |

The essential spectrum of relativistic multi-particle operators RT Lewis, H Siedentop, S Vugalter Annales de l'IHP Physique théorique 67 (1), 1-28, 1997 | 48 | 1997 |

Singular differential operators with spectra discrete and bounded below DB Hinton, RT Lewis Proceedings of the Royal Society of Edinburgh Section A: Mathematics 84 (1-2 …, 1979 | 43 | 1979 |

A geometric characterization of a sharp Hardy inequality RT Lewis, J Li, Y Li Journal of Functional Analysis 262 (7), 3159-3185, 2012 | 37 | 2012 |

The discreteness of the spectrum of self-adjoint, even order, one-term, differential operators RT Lewis Proceedings of the American Mathematical Society, 480-482, 1974 | 36 | 1974 |

Hardy and Rellich inequalities with remainders WD Evans, RT Lewis J. Math. Inequal 1 (4), 473-490, 2007 | 35 | 2007 |

On the number of negative eigenvalues of Schrödinger operators with an Aharonov–Bohm magnetic field AA Balinsky, WD Evans, RT Lewis Proceedings of the Royal Society of London. Series A: Mathematical, Physical …, 2001 | 33 | 2001 |

Necessary and sufficient conditions for the discreteness of the spectrum of certain singular differential operators CD Ahlbrandt, DB Hinton, RT Lewis Canadian Journal of Mathematics 33 (1), 229-246, 1981 | 30 | 1981 |

Some geometric spectral properties of N-body Schrödinger operators WD Evans, RT Lewis, Y Saitō Archive for rational mechanics and analysis 113 (4), 377-400, 1991 | 23 | 1991 |

Non-self-adjoint operators and their essential spectra WD Evans, RT Lewis, A Zettl Ordinary differential equations and operators, 123-160, 1983 | 21 | 1983 |

Counting eigenvalues using coherent states with an application to Dirac and Schrödinger operators in the semi-classical limit WD Evans, RT Lewis, H Siedentop, JP Solovej Arkiv för matematik 34 (2), 265-283, 1996 | 20 | 1996 |

On the number of bound states of a bosonic*N*-particle Coulomb systemV Bach, R Lewis, EH Lieb, H Siedentop Mathematische Zeitschrift 214 (1), 441-459, 1993 | 20 | 1993 |

Positive functionals and oscillation criteria for second order differential systems GJ Etgen, RT Lewis Proceedings of the Edinburgh Mathematical Society 22 (3), 277-290, 1979 | 19 | 1979 |

Oscillation and nonoscillation criteria for some self-adjoint even order linear differential operators RT Lewis Pacific J. Math 51, 221-234, 1974 | 19 | 1974 |