August 2006


This quite recently published article examines subject coverage in Google Scholar:

Neuhaus, Chris, (2006) Ellen Neuhaus, Alan Asher and Clint Wrede The Depth and Breadth of Google Scholar: An Empirical Study
Portal: Libraries and the Academy Vol. 6, No. 2, pp. 127-141.

From 47 databases 50 article titles were randomly collected from each database and compared with Google Scholar. Look at the figures here:

Conclusions: Each databse of 47 (with 2350 randomly selected articles) had a median and average coverage of 60%.

Neuhaus et al means GS weaknesses in subject coverage are social science and humanities databases and strenghts science and medical databases, open access databases, and single publisher databases.

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Web of Science have introduced a feature called Refine your results which is displayed in top of each search. Check this screenshot:

There are several options for refining, for example institutions. When searching for Haglin L as author you get 11 hits and when clicking Institutions 8 alternative addresses:

The problem is:

1) You won’t always see the name of the department in the overview, even if it’s in the record. You have to click the record to view it.

2) You will get all affiliations for all authors of all articles, not just for the author you searched or the first author name. Addresses are mixed together for all authors.
Positive is you get a better overview of different spelled addresses for authors.

Refining option Subject categories is not a subject search limit I recommend. It’s built upon the subject categories of the journals where articles is published. Sometimes you can see an option for Concept Codes or Descriptors or Controlled Index. It’s connected to content from the database BIOSIS and should not be used as an multidisciplinary subject search. These are options in development and will see in future what it can bring.

Conclusion: A better, faster overview, though same problems exist with lacking address/author information.

Google Scholar has released an option for searching Related Articles, similar to PubMed Related Articles and other databases. Google Scholar is not using a thesaurus as PubMed do, but in advanced search you can limit to 7 broad subjects. With these Related Articles option you can try to search an article of your topic. Maybe you know the title or the author. When you find the article click on the link beneath it. Check this article reference by Judit Bar-Ilan about search engines evaluation:

Clicking the Related Articles link returns 99 related articles and one is for example Greg Notess’ old (yes, 2000 is old in the search engine evaluation world!) article about Search engines inconsistencies from the magazine Online.

I also tried some other smaller subjects within information science and it returns remarkably relevant hits. Nice satisfying option, but my brief evaluations doesn’t say anything about coverage of course. When trying to subject search Google Scholar (which as I said is not easy to do comprehensive) try to use the related articles, beside of free-text searching.

Web of Science have launched Author Finder and Scopus has of course launched Author Identifier. Both tools are supposed to assist when there are lots of variants in author listings. In this news flash Authors, Authors: Thomson Scientific and Elsevier Scopus Search Them Out by Barbara Quint at InformationToday.com 24 July 2006 you can read more about these tools.

So let’s do some evaluations of these tools by using examples from my other Author-address search evaluations in Web of Science and Scopus. Let’s try my extreme author search example on Rantapaa-Dahlqvist, S. This is a screenshot from Web of Science when searching Rantapaa in Author Index which I usually suggest to use to get more complete author searches:

Here’s a screenshot of the first step in using Author Finder in Web of Science entering the last name and first initials Rantapaa-Dahlqvist, S.:

Step 2 displays author variants. But in this case Author Finder can’t find misspelled variants of the last name, just variants of first name initials. Both 51 records of Rantapaa-Dahlqvist, S and 1 record of Rantapaa-Dahlqvist, SSRD is retrieved:

Step 3 gives you the option to choose subject categories. Those categories are based on the subject of the journal published in, not the article itself:

Step 4 is a valuable refine option called Select Institution. Here you can choose the author affiliation, but it’s not always possible to refine on department level, even if the department exist on the record. The confusing thing here is that you get all the affiliations of all authors of all articles, not just for the author you’re searching. One benefit with this refine option (which also exist in Refining you results) is you get a list of possible synonym addresses and misspelled or incomplete addresses also. If you use this option to refine your search you must be aware that all records are not complete with author addresses and refining can make you loose important records:

Let’s try searching for Stegmayr, B. You get options for Stegmayr BG and Stegmayr BK also. If you choose all variants: Stegmayr, B, Stegmayr, BG, Stegmayr, BK you get 236 records. Trying to refine in step 3 by address is just such a mess because all the author addresses from the articles are displayed. Both Stegmayr are active at the same university department. Stegmayr, BK has written one article with address DEPT INTERNAL MED, but when refining with that department name you get 2 other records instead.
Let’s search for Haglin, L with Author Finder and refine to address. In this screenshot we choose UNIV UMEA HOSP, UMEA UNIV, CTY COUNCIL VASTERBOTTEN, UNIV HOSP:

That search returns 7 hits which means 4 older records are not returned. Compare results here:

This is one of the records that will be missing because Haglin’s affiliation at that time was in Uppsala:

When searching Astrom, S in Author Finder in Web of Science there are lots of options for refining on affiliation level. Refining to UNIV HOSP will also retrieve Astrom, Siv at the Department of ophthalmology, not just Astrom, Sture at Nursing Deparment. There is no option to choose just UMEA or if you take UMEA UNIV you miss Astrom, Siv. But most strange is why DEPT OPHTHALMOL isn’t optional, though other deparments like DEPT MICROBIOL is displayed. It stands clear this refining option on Institution name is just a mess!!

Searching for author Bernspang B in Cited Ref search returns a list with one entry Bernsprang B also:

The entry Bernsprang B is a misspelled citation for her thesis:

When searching Author Finder you will not retrieve the misspelled Bernsprang when searching Bernspang:

Searching Lundin Olsson or Lundin-Olsson returns no hits either in General Search or Cited ref search. Searching LundinOlsson in Author Index retrieves both LundinOlsson ,L and LundinOlsson, I:

Checking the variant with I as first initial indicates it’s a incorrect citation:

Checking Scopus shows the record is not incorrect in their reference list:

So let’s check the Author Indentifier in Scopus. It’s integrated in Author Search. A search for Rantapaa-Dahlqvist returns three variants:

But truncated Rantapa* S* returns boths variants of Rantapaa-Dahlqvist and Rantapaa-Dahlquist:

But you also need to search Dahlqvist* s*:

An advantage in Scopus compared to Web of Science is the possibility to search fullength first name. But that doesn’t even help always. Searching Eriksson, Sture returns following screenshot:

Choosing first hit gives 66 records and three records are associated via Eriksson, S-E. It’s not the same person as Eriksson, Sture at Umea university. Eriksson, S-E affiliation 2001 was Falun hospital:

Hit 9 doesn’t show affiliation but when checking the hit the record has affiliation connected in the record:

Hit 2 when checking has also affiliation at the record and shows up being Eriksson, Sture at Umea university and hit 3 and 10 are Eriksson, Sture at Umea university but none of them are connected to the first hit of Eriksson, Sture with 66 records. That’s not an improvement, that’s confusing.

The good thing is though that Eriksson, Staffan (same first initial as Sture) at the same department as Eriksson, Sture is not connected here in the search for Eriksson, Sture, which is a problem in Web of Science, as they are not using fulllength first name.

Conclusion: Author finder in Web of Science could be hazardous for detecting possible misspellings of author names. The refining option of Institution Name in Author finder presents a nice overview but is really hazardous because the addresses don’t refer just to the author, instead all co-authors also! All address information is not always possible to include and excluding options are not available. I suggest using Author Index instead.

Scopus Author Identifier has some improvements, though there still are serious flaws existing. Misspellings are still a problem and not solved in this new algorithm.

Bauer et al have published two articles on citation search:Bakkalbasi N, Bauer K, Glover J, Wang L (2006)
Three options for citation tracking: Google Scholar, Scopus and Web of Science Biomedical Digital Libraries, Vol. 3, No. 7, 29 June.

Bauer K and Bakkalbasi N (2005) An Examination of Citation Counts in a New Scholarly Communication Environment
D-Lib Magazine, Vol. 11, No. 9.

Noruzi also made some brief evaluations in an article:

Noruzi, Alireza Google Scholar: The New Generation of Citation Indexes
LIBRI Vol. 55, Iss. 4, p. 170-80
Belew K compared citation search in WoS and Google Scholar:

Belew, RK (2005) Scientific impact quantity and quality: [PDF] Analysis of two sources of bibliographic data.
Arxiv.org

The first article of Bauer and Bakkalbasi showed the citation count for GS was higher than WoS and Scopus for 2000. But for 1985 WoS seem to be best to cover citations. Comparing WoS and Scopus, WoS found more citations for 1985 but for 2000 it was similar.

The next article of Bauer, Bakkalbasi et al evaluated journal articles from two disciplines: oncology and condensed matter physics (CM physics) and two years: 1993 and 2003.

Their conclusion is:”This study did not identify any one of the three tools studied to be the answer to all citation tracking needs”. Scopus shows strength for oncology articles from 2003, but WoS performed better for CM physics and was better for both disciplines published in 1993. GS returned smaller number but had a large set of unique citing material for 2003. Bauer, Bakkalbasi et al make clear:”…it is clear that Google Scholar provides unique citing material.”

The article by Belew compares GS with WoS by author search. Belew randomly selected six academics from same interdisciplinary department and bibliographies of all publications by these authors were manually reconciled against 203 references found by one or both systems. WoS discovered 4741 citations and GS 4045, but when evaluating each author 2 authors get significantly more citations in GS.

Belew indicates that because of the quality in some bibliographic citations it’s common to find that same publication has been treated as more than one record. When searching cited ref search in WoS for an author you can find these types of errors. As Belew indicates in Table 1. With these types of errors it’s possible to loose citations for an article in WoS, but instead there are sometimes duplicates of an article (preprint and original article) that inflates citation count. Belew does not discuss that GS often shows duplicates and sometimes if you manually check the number of times cited it’s incorrect displayed.

Belew conclusion is: “GS seems competitive in terms of coverage for materials published in the last twenty years; before then WoS seems to dominate”.

We also earlier this year made a small test between Scopus and WoS by searching author name, but just author names that we can sort out as unique.

Noruzi made free text searches when testing citation search with search statement: webometrics OR webometric. Freetext search is not a proper subject search. As Bauer et al is pointing out WoS, GS and Scopus databases processes a freetext search in different ways. For example Google Scholar indexes even the fulltext of articles in contrary to WoS and Scopus. Though in this case Noruzi still have just compared each known article, though the method of choosing articles and the low amount of articles may be arguable.

None of Belew and Bauer et al have discussed the problems with citation counting in Google Scholar. Though Peter Jacso have criticized Bauer et al and presented examples of flaws in Google Scholar:

Jacso, Peter ([2005b]) Google Scholar and The Scientist
(Published on university homesite as extra material). [online] http://www2.hawaii.edu/~jacso/extra/gs/
I believe the percentage of flaws in Google Scholar may not decrease the value of the findings significantly of Belew and Bauer et al but it should be considered and discussed. Research on the propotions of citation counting flaws in Google Scholar would be of considerable value for future evaluations.

I checked the citation counting in Google Scholar of the first article Noruzi refers to in his test in Table 2:

C Almind and P. Ingwersen Informetric analyses on the world wide web Journal of Documentation Vol. 54 Iss. 4, p. 404-426

Check tihis screenshot:

I received 4 hits where the first hit clusters 11 duplicates (look at link group of 11). 3 duplicates (hit 2-4) are unclustered. Together it’s 192 citations for the article of Almind et al. But if you check the reliance of citations in all hits you will find duplicates. I evaluated maually all 192 citations together and found 13 obvious duplicates. It’s manually checked and some more duplicates may be found. All records in chinese letters are not checked. Here are screenshots on all duplicates put together with an image editing software:

Of 192 citations from GS, 12 is duplicates which gives these results: GS 180, WoS 90. This means 6% is incorrect citations.

Of course WoS could have duplicates also.

Conclusion: Scopus is important for finding more citations from 1996 and current. Google Scholar is important because it finds a lot of unique citations but each reference with information on times cited should be manually checked by counting and looking for duplicates. Web of Science is still competetive, especially for older material.

As Noruzi mention in his article GS indexes a lot more of publication types and from various languages. If every citation, no matter from which source, has the same value of 100%, GS is an important source. The discussion should exceed on the value of each citation. Should self-citation get any value at all? Should articles not peer-reviewed get a lower value for their citations?

When searching this article An Examination of Citation Counts in a New Scholarly Communication Environment by K Bauer, N Bakkalbasi – D-Lib Magazine, 2005 in Google Scholar you get the result cited by 8 other papers:


When checking all this 8 papers cited the Bauer et al article you well get three citations from the same source in The Scientist “The future of citation analysis”:

Google Scholar have managed to find 4 duplicates (as you can see in the last reference in link “group of 4”) and cluster them but missed two other duplicates.