Lubis, A. I. U. . (2021) “Study Of The Effectiveness Of The Use Of Gypsum And Volcanic Ash On Stability Of The Clay Soil Based On The CBR Value And The Unconfined Compression Test”, Jurnal Mekintek : Jurnal Mekanikal, Energi, Industri, Dan Teknologi, 12(2), pp. 37–45. doi: 10.35335/mekintek.v12i2.26.