A nontransformation proof of Mann's density theorem. Betty Kvarda Garrison — 1970 Journal für die reine und angewandte Mathematik
Weak forms of Mann's density theorem extended to sets of lattice points Betty Kvarda Garrison — 1971 Acta Arithmetica
Density inequalities for a restricted sum of sets of lattice points Betty Kvarda Garrison — 1971 Acta Arithmetica