The general explanation of the symbols used is given in Meaning of Symbols. The specific notes
relating to this article are:
This is an important article and deviations which are not
merely drafting or very minor need to be noted. The differences
between the 1963 and the 1977 texts are very minor, and
compliance with 1963 generally therefore merits 
. The essential principle is that the
business profits (industrial or commercial profits) of an
enterprise of country A shall not be taxable in country B unless
the enterprise carries on business in country B through a
permanent establishment situated therein, and that the profits
of such a business shall only be taxable in country B to the
extent that they are attributable to that permanent
establishment. Any deviation from this, eg the application of a
force of attraction rule, will be symbolised by 
.
There may be additional notes on offshore oil and gas
activities. These are in general reflected by 
, but qualify for 
if the reference is only to exclude such
offshore activities from the article).
The overall picture of the extent to which countries follow
the Model is shown in the Model Article 7
Summary.