Average Co-Inventor Count = 2.40
ph-index = 2
The patent ph-index is calculated by counting the number of publications for which an author has been cited by other authors at least that same number of times.
Company Filing History:
1. Hitachi, Ltd. (2 from 42,488 patents)
2. Hitachi Systems & Services, Ltd. (2 from 4 patents)
2 patents:
1. 7047238 - Document retrieval method and document retrieval system
2. 7010519 - Method and system for expanding document retrieval information