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Google Scholar team, please bring back almost 30,000 citations of my highly cited book!

During some recent update of its service, the Google Scholar Citations, Google lost about 30,000 citations to my highly cited book "Fractional Differential Equations" (Academic Press, Inc., San Diego, 1999).

I understand that the amount of data that Google Scholar collects and processes is enormous, but it might be that I am not the only one affected by the recent update.

My Google Scholar Citations ID is: 4H2CInEAAAAJ, and my profile is:

The severely affected publication is my book (further "FDE"):

Book cover Podlubny, I.: Fractional Differential Equations. An Introduction to Fractional Derivatives, Fractional Differential Equations, Some Methods of Their Solution and Some of Their Applications. Academic Press, San Diego-Boston-New York-London-Tokyo-Toronto, 1999, 368 pages, ISBN 0125588402.


On April 22, I had a meeting with the deputy director of the Isaac Newton Institute (Cambridge, UK), and on that day my FDE book had 31,761 citations.

However, two months later, on June 20, the Google Scholar showed only 2,419 citations to my FDE book -- less by almost 30K lost citations (29,342 citations have been lost, to be precise)... And on August 28, 2022, the Google Scholar still shows only 2547 citations to this book... !

This is obviously wrong, because:

Web of Science: 20,497 citations (August 9, 2022)

To find citations to my book in the Web of Science, the "CITED REFERENCES SEARCH" must be used. On August 8, 2022, there were 20,497 references to my book in the papers indexed by the Web of Science. See the video below.

In the end of the video recording you can see that, according to the Web of Science analysis, my FDE book is cited in 133 different fields of science, and the number of its citations only in the single year 2021 is 2,497...

Scopus: 22,083 citations (August 9, 2022)

In Scopus, the "Search within [References]" must be used. On August 8, 2022, there were 22,083 references to my book in the papers indexed by Scopus. See the video below.

Mathematical Reviews (MathSciNet): 5,320 citations (August 19, 2022)

According to MathSciNet (Mathematical Reviews, online) database maintained by the American Mathematical Society, my book "Fractional Differential Equations" currently has 5,320 citations in the works indexed by MathSciNet, and is the most cited mathematical book of the decade 2012-2021, being #1 in 2012-2014 and 2017-2021, #2 in 2016, #4 in 2015.

Even those 5,320 citations indexed in MathSciNet with its narrow mathematics-only scope is two times more than the number of citations of my book shown by the Google Scholar on August 28, 2022.

Archived Google Scholar Citations at WayBackMachine: 31,113 citations (March 5, 2022)

After noticing that a huge number of citations to my book disappeared from my Google Scholar Citations profile, I tried to see if Internet Archive ( eventually has any archived copies of my profile. And it had some copies; the latest is dated March 5, 2022 (strangely, in Swedish language), with 31,113 citations to my book.

Where to look for errors?

Go to Google Scholar, and search for [ podlubny "fractional differential equations" ], as shown in the video below. This will return only one strange item...

My hypothesis is the following. As far as I understand, the Google Scholar more or less periodically performs updates of its dataset, and then runs its algorithms for processing the publications and citations on that updated dataset. Most probably there is an error at the stage of the dataset update.

The probability of my book being the one-and-only affected publication is zero (however, remember that zero probability of an event does not mean that the event is impossible). Finding an error and fixing it might most probably help other researchers, too.

I hope that it will be possible to fix the problem with citations to my FDE book soon during the update of the otherwise excellent Google Scholar Citations product. The Google Scholar plays already an extremely important role in the scientific community, for doing research and for evaluating research performance, and it must work as reliably as possible.

Igor Podlubny,
August 28, 2022.