Please answer the following question: Information:  - Bulgaria (tr. '), officially the Republic of Bulgaria (tr. '), is a country in southeastern Europe. It is bordered by Romania to the north, Serbia and Macedonia to the west, Greece and Turkey to the south, and the Black Sea to the east. With a territory of , Bulgaria is Europe's 16th-largest country.  - Cherni Vrah (/ Black Peak) is the summit of Vitosha Mountain in Bulgaria. Rising to 2290 m, the peak is the fourth highest mountain summit in the country after Musala (2925 m, Rila Mountains), Vihren (2914 m, Pirin Mountains), and Botev Vrah (2376 m, Balkan Range).  - Serbia, officially the Republic of Serbia, is a sovereign state situated at the crossroads of Central and Southeast Europe, covering the southern part of the Pannonian Plain and the central Balkans. Relative to its small territory, it is a diverse country distinguished by a "transitional" character, situated along cultural, geographic, climatic and other boundaries. Serbia is landlocked and borders Hungary to the north; Romania and Bulgaria to the east; Macedonia to the south; and Croatia, Bosnia-Herzegovina, and Montenegro to the southwest; it also claims a border with Albania through the disputed territory of Kosovo. Serbia numbers around 7 million residents, and its capital, Belgrade, ranks among the largest cities in Southeast Europe.  - Romania is a sovereign state located in Southeastern Europe. It borders the Black Sea, Bulgaria, Ukraine, Hungary, Serbia, and Moldova. It has an area of and a temperate-continental climate. With 19.94 million inhabitants, the country is the seventh-most-populous member state of the European Union. The capital and largest city, Bucharest, with its 1,883,425 inhabitants is the sixth-largest city in the EU.  - Malak Rezen ( Bulgarian :   / `` Little Slice '' ) is a peak rising to 2,191 m in northeastern Vitosha Mountain in Bulgaria . The peak is situated 1.5 km northeast of the summit Cherni Vrah , and 1.3 km north by east of Golyam Rezen Peak , surmounting Stenata ski run and Aleko site to the north . Malak Rezen is accessible by the Romanski chair lift , and serves in turn as a convenient starting point for the three highest peaks of Vitosha Mountain -- Cherni Vrah ( 2,290 m ) , Golyam Rezen ( 2,277 m ) , and Skoparnik ( 2,226 m ) . Rezen Knoll on Livingston Island in the South Shetland Islands , Antarctica is named for the peaks of Malak Rezen and Golyam Rezen .  - Musala (from Arabic through Ottoman Turkish: Musalla, "near God" or "place for prayer" is the highest peak in the entire Balkan Peninsula, standing at 2,925 m (9,596 ft). The summit of the Rila mountain range in southwestern Bulgaria, Musala is the highest peak between the Alps and the Caucasus and the highest in Eastern Europe bar the Caucasus. With a prominence of 2473 m, Musala is the 7th most prominent mountain peak in Europe.  - Vihren is the highest peak of Bulgaria's Pirin Mountains. Reaching , it is Bulgaria's second and the Balkans' third highest, after Musala and Mount Olympus. The peak is located in Pirin's northern parts. The easiest route is from the Vihren chalet (2,000 m), reaching the summit from the south. Other routes include those from Banderitsa chalet (1,800 m) or across the ridge Koncheto from the north. A number of Pirin's lakes are located around the peak, as is Europe's southernmost glacial mass, the Snezhnika glacielet.  - Bistrishko Branishte is a nature reserve on Vitosha Mountain in Bulgaria comprising the eastern slopes of Golyam Rezen (2277 m), Malak Rezen (2191 m) and Skoparnik (2226 m) Peaks, the northern slopes of Golyam Kupen Peak (1930 m), and the upper valleys of Vitoshka Bistritsa River and Yanchevska River. Surface area 1061.6 ha, elevation between 1430 and 2277 m.  - The Black Sea is a body of water between Eastern Europe and Western Asia, bounded by Bulgaria, Georgia, Romania, Russia, Turkey, and Ukraine. It is supplied by a number of major rivers, such as the Danube, Dnieper, Rioni, Southern Bug, and Dniester. The Black Sea has an area of (not including the Sea of Azov), a maximum depth of , and a volume of . It is constrained by the Pontic Mountains to the south and by the Caucasus Mountains to the east, and features a wide shelf to the northwest. The longest east-west extent is about .  - A nature park or natural park is a landscape protected by means of long-term planning, use and agriculture. These valuable landscapes are preserved in their present state and promoted for tourism purposes.  - The Balkan Peninsula, or the Balkans, is a peninsula and a cultural area in Eastern and Southeastern Europe with various and disputed borders. The region takes its name from the Balkan Mountains that stretch from the Serbia-Bulgaria border to the Black Sea.  - Golyam Rezen (/ Big Slice) is a peak on Vitosha Mountain in Bulgaria. Rising to 2,277 m, the peak is second to the mountain's summit Cherni Vrah situated 900 m to the west. Golyam Rezen hosts an Air Traffic Services facility, as well as military communications installations. The precipitous east slopes of the peak are a popular rock climbing site, overlooking Bistritsa River Valley in Bistrishko Branishte Biosphere Reserve.  - Skiing is a mode of transport, recreational activity and competitive winter sport in which the participant uses skis to glide on snow. Many types of competitive skiing events are recognized by the International Olympic Committee (IOC), and the International Ski Federation (FIS).  - Vitosha, the ancient "Scomius" or "Scombrus", is a mountain massif, on the outskirts of Sofia, the capital of Bulgaria. Vitosha is one of the symbols of Sofia and the closest site for hiking, alpinism and skiing. Convenient bus lines and rope ways render the mountain easily accessible. Vitosha has the outlines of an enormous dome. The territory of the mountain includes Vitosha nature park that encompasses the best known and most frequently visited parts. The foothills of Vitosha shelter resort quarters of Sofia; Knyazhevo quarter has mineral springs. Vitosha is the oldest nature park in the Balkans. The mountain emerged as a result of volcanic activity and has been subsequently shaped by the slow folding of the granite rock layers and a series of gradual uplifts of the area. It appears dome shaped at first sight, but the mountain, 19 km long by 17 km wide, actually consists of concentric denudational plateaus rising in tiers one above the other. Vitosha is separated into four main parts whose main ridges gather at a crown known as "Cherni Vrah" (""Black Peak""). This is the highest point of the mountain at 2290 m and is one of 10 peaks of Vitosha over 2000 m in height.  - Sofia (or or ;) ("Sofiya",) is the capital and largest city of Bulgaria. The city has a population of 1.26 million, while 1.68 million people live in its metropolitan area. The city is located at the foot of Vitosha Mountain in the western part of the country, within less than drive from the Serbian border. Its location in the centre of the Balkan peninsula means that it is the midway between the Black Sea and the Adriatic Sea, whereas the Aegean Sea is the closest to it.  - Greece (' ), officially the Hellenic Republic (Greek: ' ), historically also known as Hellas ("" ), is a country in southeastern Europe.  Greece's population is approximately 10.955 million as of 2015. Athens is the nation's capital and largest city, followed by Thessaloniki.  - Turkey, officially the Republic of Turkey (Turkish: ), is a transcontinental country in Eurasia, mainly in Anatolia in Western Asia, with a smaller portion on the Balkan peninsula in Southeast Europe. Turkey is a democratic, secular, unitary, parliamentary republic with a diverse cultural heritage. Turkey is bordered by eight countries: Greece to the west; Bulgaria to the northwest; Georgia to the northeast; Armenia, the Azerbaijani exclave of Nakhchivan and Iran to the east; and Iraq and Syria to the south. The Aegean Sea is to the west, the Black Sea to the north, and the Mediterranean Sea to the south. The Bosphorus, the Sea of Marmara, and the Dardanelles, which together form the Turkish Straits, divide Thrace and Anatolia; they also separate Europe and Asia. Turkey's location has given it geopolitical and strategic importance throughout history.    Given the paragraphs above, decide what entity has the relation 'located in the administrative territorial entity' with 'sofia'.
A:
malak rezen