Issued Patents 1989
Showing 1–2 of 2 patents
| Patent # | Title | Co-Inventors | Date |
|---|---|---|---|
| 4854102 | Sub-roof for a roof covered with roofing boards | Eugen Feil, Wolfgang Graser, Horst Friedrich | 1989-08-08 |
| 4800675 | Roofing plate for planting greenery on roofs | Eugen Feil, Wolfgang Graser, Horst Friedrich | 1989-01-31 |