Some weeks ago Ulf Sundberg's dissertation Swedish defensive fortress warfare in the Great Northern War 1702-1710 was published. A lot can be said of this work, but I will focus on one point:
Sundberg starts by emphasizing the importance of Karolinska krigares dagböcker and Historiska handlingar and then goes on to state that the most important published Russian source is the so called diary of the Czar, which Sundberg has used in a edition from 1773. In my opinion that's a remarkable statement given the existence of Pisma i bumagi, literally thousands of pages of letters from and to the Czar.
As for the Baltic archives Sundberg states that the "General Governor's archive in Tartu [Estonian: Riigi Keskarhiiv, Swedish "Estlands centralarkiv i Tartu"] is worth mentioning, because "it has several documents from commanding officers in Swedish Livonia". But Sundberg didn't use these documents as Fredrik Arfwidsson did so in the 1930's. Well, "several documents" is a bit of an understatement. I have up til now registered about 15,000 incoming letters (most of them from the period in question) and then there is an enormous amount of copies of outgoing correspondence. I would argue that it is not possible to write about Livonia during the GNW without using the archive of the Governor General (which apparently unbeknownst to Sundberg became divided between Tartu and Riga after World War 2). As for Tartu the Archive haven't been called "Riigi Keskarhiiv" for a very long time. The wording suggests to me that Sundberg hasn't really made an effort to check what the archive contains and certainly isn't aware that the part preserved in Riga was microfilmed in the 1990's - and the films available in Stockholm.
Another part of Sundberg's work should depend on Danish sources, but he says that he abstained from using Danish archives because he presumed that Bidrag til den store nordiske krigs historie had used everything that wasn't difficult to find...
Sundberg has also left Russian archives aside because of language difficulties. Even if that is to be considered understandable, it's rather unfortunate when the topic of the dissertation so clearly focuses on events involving Russian forces. So if not archives - how about Russian literature? Surely in this day and age it would not only have been possible to consult the most relevant works, but also to have the key parts translated?
Sundberg's bibliography has a few notable omissions, for example Carl von Rosen's Bidrag till kännedom. I also miss the series "Skrivelser till Konungen", which I would think is pretty central for any work on the GNW.