Twin Grid Files: A Performance Evaluation. - Andreas Hutflesz; Peter Widmayer; Hans-Werner Six (Workshop on Computational Geometry, 1988)

The Twin Grid File: A Nearly Space Optimal Index Structure. - Andreas Hutflesz; Hans-Werner Six; Peter Widmayer (EDBT, 1988)

Globally Order Preserving Multidimensional Linear Hashing. - Andreas Hutflesz; Hans-Werner Six; Peter Widmayer (ICDE, 1988)

Twin Grid Files: Space Optimizing Access Schemes. - Andreas Hutflesz; Hans-Werner Six; Peter Widmayer (SIGMOD Conference, 1988)

The R-File: An Efficient Access Structure for Proximity Queries. - Andreas Hutflesz; Hans-Werner Six; Peter Widmayer (ICDE, 1990)