Original: When Hooper fell into financial difficulties, the Britannica was managed by Sears Roebuck for roughly 18 years (1920 - 1923, 1928 - 1943).
Simplified: When Hooper had financial problems, the Britannica was managed by Sears Roebuck for about 18 years (1920 - 1923, 1928 - 1943).