It's HTML character references for encoding a character by its decimal code point. Look at the ASCII table here and you'll see that 39 is the code for apostrophe.

L'

6 Aug 2012 http://www.furiousearth.com "Angry Planet" host George Kourounis goes on a hair raising flight in an L-39 Albatross fighter jet, experiencing  ANALYSIS: How Aero Vodochody recharged the L-39 25 Feb 2019 Most of the pilots who honed their combat skills in the Aero Vodochody L-39 Albatros single-engined jet trainer were defending the Soviet  39 CFR § 232.1 - Conduct on postal property. | CFR | US Law ... (l)Weapons and explosives. Notwithstanding the provisions of any other law, rule or regulation, no person while on postal property may carry firearms, other 

The Aero L-39 Albatros is a high-performance jet trainer developed in Czechoslovakia by Aero Vodochody. It was designed during the 1960s as a replacement  Aero L-39 Albatros — Википедия Аэро Л-39 «Альбатрос» (Aero L-39 Albatros, Элли) — чехословацкий учебно-боевой самолёт. Создан для замены учебно-тренировочного самолёта 

Aero L-39 Albatros — Википедия

Aero L-39 Albatros - Wikipedia The Aero L-39 Albatros is a high-performance jet trainer developed in Czechoslovakia by Aero Vodochody. It was designed during the 1960s as a replacement  Aero L-39 Albatros — Википедия

ANALYSIS: How Aero Vodochody recharged the L-39

39 CFR § 232.1 - Conduct on postal property. | CFR | US Law ...