$^0$Manisha ma’am’s gc resources
$^1$Arka sir’s gc resources
$^2$https://www.alevelgeography.com/coastal-system/
$^3$https://geo.libretexts.org/Bookshelves/Geography_(Physical)/The_Physical_Environment_(Ritter)/02:_The_Earth_System/2.03:_Natural_Systems/2.3.02:_Types_of_Systems
$^4$https://www.brainkart.com/article/Stages-of-the-River_33784/
$^5$https://www.alevelgeography.com/the-long-profile/
$^6$https://slideplayer.com/slide/10761159/
$^7$https://www.alevelgeography.com/the-long-profile-changing-processes-types-of-erosion-transportation-and-deposition/
$^8$https://www.bbc.co.uk/bitesize/guides/zq2b9qt/revision/2
$^9$https://sciencing.com/factors-affecting-rivers-velocity-8223150.html
$^{10}$http://thebritishgeographer.weebly.com/river-landforms.html
$^{11}$https://www.geologyin.com/2014/03/drainage-pattern.html
$^{12}$https://www.alevelgeography.com/waves/
$^{13}$https://www.alevelgeography.com/transportation/
$^{15}$https://www.alevelgeography.com/river-discharge-storm-hydrograph/