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'

История создания и характеристики учебно-боевого ... 18 окт 2018 ТАСС-ДОСЬЕ. 18 октября 2018 года в Минобороны РФ сообщили, что учебный самолет Л-39 (Aero L-39 Albatros) военного ведомства  Flight in an L-39 Fighter Jet - YouTube 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  L-39 Jet Flight in Russia - including outside cameras! - YouTube 4 Oct 2018 L-39 Flight near Moscow, Russia. The flight in Kaluga is with a Russian Air Force veteran in the rank of a colonel. As you can see from this  39 CFR § 232.1 - Conduct on postal property. | CFR | US Law ...

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 Аэро Л-39 «Альбатрос» (Aero L-39 Albatros, Элли) — чехословацкий учебно-боевой самолёт. Создан для замены учебно-тренировочного самолёта  Aero L-39 Albatros - Wikipedia

L'Aero L-39 Albatros è un monomotore a getto da addestramento avanzato ad alte prestazioni, prodotto dall'azienda cecoslovacca Aero Vodochody negli anni ...

Flight in an L-39 Fighter Jet - YouTube 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  L-39 Jet Flight in Russia - including outside cameras! - YouTube 4 Oct 2018 L-39 Flight near Moscow, Russia. The flight in Kaluga is with a Russian Air Force veteran in the rank of a colonel. As you can see from this  39 CFR § 232.1 - Conduct on postal property. | CFR | US Law ...

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

...  Unused Space ! Exclamation mark " Quotation mark &# 35; Number sign $ Dollar sign % Percent sign & Ampersand ' ... Aero L-39 Albatros – Wikipedia, wolna encyklopedia L-39 Albatros – odrzutowy samolot szkoleniowy produkcji czechosłowackiej firmy Aero Vodochody, wprowadzony do użytku na przełomie lat sześćdziesiątych i ...