I cannot link. But try searching Polish wiktionary Aneks deklinacja. Go to the source. Did you try your book? There is also a link to Polish grammar in the nutshell somewhere in forum.
Y never comes after G and K so I is used, these Is vanish in other forms (dłogą, drugami) but remain for E (wąskiego, wysokiemu)
Some adjectives are soft and most them ends in ni (tani, ostatni). These Is retain in all cases. An important exception is trzeci (third), which is also soft.