Question on the usage of the word "THE"

Definite grammatical article that implies necessarily that the entity it articulates is presupposed; something already mentioned, or completely specified later in the same sentence, or assumed already completely specified. Compare I'm reading a book with I'm reading the book. --Wiktionary (best and most concise dictionary ever IMO)

I think we can immediately rule out the possibility that the entity preceding "the" cannot be presupposed in a research paper, except for certain evident cases.

Ok, the author of the following makes a rather peculiar usage of the word "the":


Moreover, it may be difficult to separate the effects
of salt from other nutrients that may contribute to
stomach cancer risk. The absence of adjustment for
confounding factors (such as age, sex, smoking and
dietary habit) can hamper the statistical estimation
causing over- or underestimation of the real association
between salt or salted food and stomach cancer. In
Tables 1 and 2, few studies have controlled for dietary
factors in their analyses of salt consumption, which
makes it difficult to compare the different studies
according to the dietary variables adjusted in the analysis.
However, the study results that were adjusted by a wide
range of potentially confounding variables, such as age,
sex, H pylori infection, atrophic gastritis, medical history
of peptic ulcer, family history of cancer, body mass
index, diabetes, total cholesterol, physical activity, alcohol
intake, smoking habit and other dietary factors[68],
showed no difference from the crude results. Studies
with adjustment for some or most of the above potential
confounding factors[66,68,72,73] showed no systematically
apparent differences from the studies with adjustment
for a few or several confounders.

The first "the" was meant to precede "analysis" as in the analysis of the research soon-to-be mentionned.

The word preceding the second "the" is specified in the REFERENCES ([68]). Is this grammatical?