@article{ckppt-dpsht-17
, author =        "Colin~de Verdi\`{e}re, {\'E}ric and
                   Kalu\v{z}a, Vojt\v{e}ch and Pat{\'a}k, Pavel and
                   Pat{\'a}kov{\'a}, Zuzana and Tancer, Martin"
, title =         "A direct proof of the strong {H}anani--{T}utte
                   theorem on the projective plane"
, journal =       "Journal of Graph Algorithms and Applications"
, volume =        "21"
, number =        "5"
, pages =         "939--981"
, year =          "2017"
}