Complex sentence: These 19th-century abbreviations, originally used in telegraphy and typewritten memos, fell out of use in the early 20th century; however, J.K. has recently been revived as an Internet abbreviation.
Split into simpler sentences: These 19th-century abbreviations were originally used in telegraphy and typewritten memos, but fell out of use in the early 20th century. However, J.K. has recently been revived as an Internet abbreviation.