15984778_Astronomy___Astrophysics__A_A__ti_word_verbs_and_expressions__Error_
[The phrase to question] Variation of/in To vary by OF indicates the amount of variation while IN indicates what is varying, not(y) by how much: "a variation in amplitude of 5%"; the verb use: "The amplitude varies by 5%" [Error?] 
x
x
M
R
x , R
I
Astronomy & Astrophysics (A&A)
Error?