Lipton’s Journal/February 10, 1955/560
From Project Mailer
Investigating the consonants I’ve found some fascinating material. R and L are the only consonants which combine with any frequency with other consonants at the beginning of words until one gets to S. S has many combinations. Sh, Sk, Sl, Sm, Sn, Sp, Squ, Sc, Scr, St, Str, Sw. No doubt about it, R, L, and S are the key consonants in English.