Spoilers are precisely defined here. Rules vary by the story's medium. Info from television stories can't be added here until after the top or bottom of the hour, British time, closest to the end credits roll on BBC One. Therefore, fans in the Americas who are sensitive to spoilers should avoid Tardis on Sundays until they've seen the episode.
Additional Input: Letters Page (From DWM 47): The letters page queries the cover caption of 'four foes' but five shown. Not admitting to error, the explanation is given that the Ambassadors of Death were "...not really an enemy at all so the cover caption was right... wasn't it?"
The year is not included on the front cover, which had a cover price of 30p (UK).