useless trivia: What Word Means: Of A Nidus?

Questions

03 February 1973 Dr ---------- 's "Cover of "Rolling Stone"" enters Top 40 & peaks at #6 ?

08 February 1973 Senate names 7 members to investigate ---------- scandal ?

11 February 1973 1st one-day international for Pakistan & ---------- ?

16 February 1973 West Indies vs Australia at---------- , 1st time since 1955 without Sobers ?

21 February 1973 Israeli fighters shoot ---------- aircraft down, killing 108 ?