The original post was from Marco Ferrari but i intend to make some slight changes to his post. The magazine "Musica & Som" from that period are monthly and sometimes bimonthly or quarterly but in the top of the charts there's an indication of the month (so the date is only the end of the period).
There are some missing charts because the magazine don't include charts or because the period was bimonthly or trimontlhy. In the first charts of the decade the charts include the number of weeks but afterwards they changed to the number of months. In some magazines is possible to know the positions of the previous month. It's the reason because there are charts with some missing positions.
The weekly charts begun to be published in "TV Top" in early 1981 but before were published in "Top Musica & Som" (not to confuse with "Música & Som") that was published separatedly with newspaper "Correio da Manhã". I think that some of the charts published in "Billboard" were the weekly ones ("What's Another Year").
, thank you very much for the charts posted. How do you know the dates of monthly charts? Are they from the magazines or you somehow chose those dates? Will be thankful if you can explain
Música & Som - Music Magazin founded in Feb 1977. In the first years it was published fortnightly but later it was published monthly. Some issues could be bimonthly or quarterly.
Top Música & Som - Small Weekly Music Magazine - Founded in Nov 1978. In 1980 it was incorporated as a weekly supllement of "Correio da Manhã" (on sundays).
TV Top - Television Magazine that begun in 1981 and included the weekly charts