Reference:

Matthias Hopf, Michael Luttenberger, and Thomas Ertl. Hierarchical splatting of scattered 4d data. IEEE Computer Graphics and Applications, 24(04):64–72, 2004.

Suggested BibTeX entry:

@article{g4hopf,
    author = {Matthias Hopf and Michael Luttenberger and Thomas Ertl},
    journal = {IEEE Computer Graphics and Applications},
    number = {04},
    pages = {64--72},
    title = {Hierarchical Splatting of Scattered 4D Data},
    volume = {24},
    year = {2004}
}